My Mac is old and needs upgrading, it cannot be upgraded any more to take the various software I need for every thing I do.
The cost of a new Mac is a fair bit more than what I would pay for a Pc so I am considering going with the Pc.
I am using imovie at the moment and eventually would upgrade to Final cut pro x mainly because the interface looks similar, but I am very unsure which editing software to go for if I decided on the Pc route.

As somebody who only recently made the jump TO a Mac, the differences are in reality not as significant as people make them out to be, unless you are interested in what goes on inside.

Windows will annoy you at times, mainly because it isn't very friendly - and most of it's warning messages make you think doom and gloom even when the warning is virtually worthless.

The real practicalities of the swap are that final cut is lost to you - some software really is machine specific. Oddly, windows users can run all their windows software on macs - I've had no problem running parallels for my windows only software that I am loath to give up. Adobe on Mac and PC differences are mainly just where a few features are located - that's all. Windows 7 is a perfectly workable operating system, so I suspect that buying a fast well equipped PC won't make you that cross once you get used to the basic differences. Mind you, a fast well equipped PC isn't that cheaper than a Mac? The lower spec machines in windows land don't have a direct equivalent, so you could discover that things that make you cross on windows are not really down to windows - they're down to it being a cheap PC. Personally - knowing what I have picked up since christmas, there is no way I'm going to go back to video on a PC. On the PC I hated Soundbooth, using alternatives for audio. However, on the Mac, I had no choice for a project, so had to use Soundbooth, and have now really got to like it!

I am very unsure which editing software to go for if I decided on the Pc route.

Upgrading a PC with a new CPU or motherboard is generally possible. At the same time the built-in monitor of the 27" iMac has resolution 2560x1440 which is less common on a PC. It is difficult to know which would be more expensive in the long run.

If you go the PC route I would suggest Sony Vegas Platinum 11 as an inexpensive but capable video and sound editor. It is frustrating to switch software, but since you are anyway switching from iMovie to something else, there is no avoiding that.

Certainly, 2560x1440 monitors are around, Dell have a 27" monitor in their range.

Certainly, 2560x1440 monitors are around, Dell have a 27" monitor in their range.

Agreed, but much of the price difference between a PC and an iMac is obtained by skimping on the monitor.

My Mac is old and needs upgrading, it cannot be upgraded any more to take the various software I need for every thing I do.
The cost of a new Mac is a fair bit more than what I would pay for a Pc so I am considering going with the Pc.
I am using imovie at the moment and eventually would upgrade to Final cut pro x mainly because the interface looks similar, but I am very unsure which editing software to go for if I decided on the Pc route.

I have never had issues with a PC, ever, and I hack a lot. The level of customization available on a PC is extraordinary, and if you make your decisions carefully, not only will you save money, but you will have a beast of a machine that will never let you down. A PC gives you the freedom to take your own decisions and you are spoiled for choice. The question to ask is: do you like being responsible for your machine? If not, stick to Apple - they love deciding what's best for you.

Right now, as far as editing is concerned, you could try Adobe Premiere Pro, Sony Vegas Pro or Edius, among others. If you are used to FCP (not FCP X), then I recommend Premiere - they are very similar in design and usage. I haven't worked with imovie so I'm not sure how the interface works.

I've also heard great things about the new Edius - just download the demos and try it for yourself. Hope this helps.

I have been using EDIUS for years.

Done huge projects and countless same day edits on it.
Native 1920/1080 25p Canon movs, Sony AVCHD, HDV 1440/1080 50i clips all together at full res and real time on my old 2008 built PC. Something even the latest MACS cannot do unless they convert it to some other huge hard drive sapping codec like ProRes lol Then you end up with two files of everything.

Making Pal and NTSC days DVD's leaves FCP / FPX for dead. From a mixed 45 minute timeline I could make both a PAL and NTSC DVD in 1 hour. Took a Quad iMac doing the same thing over 4 hours, and that was just to make the PAL version. lol And I was using a little i5 $1300 laptop too.

Thanks for the feedback.
I have a friend that biulds computers who is willing to build one for me, if I went the Pc route what system requirements do I need, do I just copy the specifcations of the imac I would buy if I went that route.

If you buy or build a pc first thing you need to know is what NLE you will be using and then build the pc around the NLE's specifications. Do you already know what you will be using? I have worked with Premiere, Vegas and now Edius. My experience is that If audio is very important part of your workflow and you need to be able to have much controll then Sony Vegas is a no-brainer, if you need different programs to interact seamlessly together then adobe is the best choice (considering you will be working with after effects, photoshop, encore ...)
If you do a lot of multicam, need a fast and very stable cutter then Edius is your best choice.

Every nle has it positive/negative sides, what I didn't like about Vegas was that is was not always stable, several times it would just dissapear and leave me staring at the desktop. Edius has limited audio capabilities, but here I just export the audio once the editing is done and finish it up in Vegas. And Premiere requires a very fast (and expensive pc) if you want to maximize it's performance. If you only buy Premiere you do get Encore with it and it works wonderfully together with photoshop but it feels kinda bloated to me which makes it slow. Therefore I"m using tmpgenc autoring works to make my blu-rays and dvd's now and that is stable and very fast.

I"d suggest, just download some trials and try out :)

...if I went the Pc route what system requirements do I need

The last thing you should do is copy-paste.

1. Make a list of all the software you will use and need over the next three years. The starting point should be a spec list that fulfills the minimum requirements of every one of them.
2. Estimate your footage specs - like resolution, data rate, project length, data size, color space, audio, etc. Any and every one of these has a direct bearing on what you should aim for.
3. Estimate your delivery requirements - tape, DVD, Blu-ray, cinema, solid state, internet, etc.
4. Estimate how much time you'll have from prep to delivery for each project

From this you will know exactly what kind of system you need to deliver on the projects you are working on. Once you have a rough estimate of your requirements, if you are still unsure, post back here for specific help.

This is probably a good place to mention that if you format an external drive with exFAT, it will work great on both Macs and PCs. Kind of like FAT32 but without the 4GB file size limit. You have to do the format on a PC, and it won't work with pre-Intel Macs or older versions of Windows, but with up to date computers it is an ideal dual platform hard disc format.

We have Macs at home and PCs at work. I switch between the two on a daily basis. Honestly, your biggest issue will not be moving from Mac to PC (they operate virtually identically) but switching from iMovie to another editing program.

I've been a Mac user since my first Mac 128 back in 1985 and a Windows user since v3.0 in 1990. Windows is not inherently more error prone than OSX, but the applications may be. That's because there's a whole bunch of crappy free and cheap software available for Windows. RESIST installing anything you don't absolutely need. Follow that simple rule and your Windows experience will be trouble-free.

I'd suggest looking at Sony Vegas Movie Studio (about $125), or if you find that limiting, you can try Sony Vegas Pro ($600). Yes, there is a learning curve (as with any software) but it's probably less than other editing software.