I think I know the answer to this question, but I have a 2006 2.66 Intel Quad Core MacPro and have the storage maxed out with 750GB drives. Originally it was stated when I purchased the MacPro that the largest disk it could take was 750GB.

Is this due to the fact that the largest disk made at that time was 750GB?

If this is so, then I should be able to install 2TB drives in the MacPro, correct?
This would be great as I am moving to AVCHD shooting (Sony NX5U) and will be transferring AVCHD footage to an external drive for backup and also to my edit drives as well. But I will also be converting all of the AVCHD footage to ProResLT for editing in FCP.

This is far from an authoritative answer but I recently successfully mounted two 1.5TB Hitachi SATA3 drives in a G5 tower (they are operating at SATA1 or 2... I can't remember which buss the G5 supports), which is of course older than your Intel box.

I have the same MacPro and I have two 1TB and two 2TB disks in there. No problems. I remember reading that too. I assume that was just the largest disks available at the time.

Thanks for the confirmation.
That's what I thought as well. I can see the RAM max being an issue, due to the motherboard.
But hard disc capacity seemed like it shouldn't be an issue with a motherboard or processor.

That's most likely the same issue in regards to a 2-drive external RAID enclosure, which also only says 1TB drives. As 1TB drives were the largest available at the time of the enclosures production.