I'm looking into buying a Fostex MR8 for recording my sound seperately when shooting. I am certain there are better sound recorders out there but at the same time this is a rather affordable piece of equipment. It is directed more toward music recording (guitar inputs and midi inputs) but the two XLR inputs allow me to use just about any high quality shotgun microphone. My main concern is impedance, and keeping it balanced between the MR8 and the microphones. Here is the datasheet for the MR8.
http://www.fostex.com/support/pdf/fostex/mr8/mr8_data_sheet.pdf

with an input impedance of 1.5k, is that around low to midrange inpedance? I'm rather new to sound but am aware that I will want to keep my impedance on the mics as close to this figure as possible. The Audio Technica microphones Im looking at have very low impedance levels which is a good thing if you want a long cable, but just how long would someone need for attaching the mic to a boom pole? I'm thinking a good 25' length would do the trick and have enough left to trail back to the recorder.

BUT...the AT835b has an impedence level of 500 ohms with phantom power and 600 with battery power. How would one balance this between the mic and recorder so no hiss is picked up? Is 600 ohms going into a recorder with an input impedance of 1.5k ohms or more aceptable? I know there are balanced cables, but I do not know much about those.

Thanks to anyone who reads this lengthy question and replies with any input!

With modern equipment these impedence values aren't going to have a practical effect. This device doesn't have phantom power on the XLR inputs, so you're limited to battery power mics unless you want to get an additional power box. Dynamic mics don't have enough sensitivity to record dialog without having the mic in the shot.
The AT897 shotgun is a good choice where a shotgun is appropriate. Many people feel it sounds smoother than the Sennheiser K6/ME66.
Other choices are the K6/ME64 cardioid, although both it and the 66 might be too hot for this mic input under loud conditions. The Rode NT3 hypercardioid has good sound but it a little large and heavy. The ATM31a is ok for a cardioid, but it is getting into the low-sensitivity range.
If you get a phantom power adapter you can use better mics.
Will this recorder have enough capacity for your needs?

according to the acrobat file, that unit only allows two track recording at one time . That means that if you wanted to use more than two sound sources, you'd need a pre mixer, and would still only end with two tracks. Of course you could add more in post. It also looks like you don't ahve a lot of record time.
Good luck
Bruce yarock

record time varies with the size of the compact flash card. You're right Bruce, the amount of recording time you get with the wimpy 128mb card that is included is not nearly enough. A 1 gig or 512mb chip will probably do the trick for me.

Jay, thanks for pointing out that phantom power issue. You've pretty much cleared up everything for me. Thanks for the advice on other mics. The AT897 looks like my best bet right now. Im investing into sound for my minute productions before any lens or filters (I cant afford everything at once.) Sound is very important to me as I just cant shoot anything meaningful and digest it fully with the current sound pickup from the XL1s mic. Thanks everyone for the advice on my situation!

also, i bought an AT 897, and I'm pretty happy with it. It's not as hot as the Senn 66, but sounds good.( I really wanted the Neuman kmr81 or the Sanken cs3, but after speaking to my "sponsor" at Gear Slutz Annon., I deceided to make a more sensible purcahse...)
Bruce Yarock