I have a Refurb Mac Pro 3.0GHz on the way, my two new Hard Drives just came in the mail today from newegg, I have not installed them or tried them out yet, as I don't have the machine...
It took a long time for me to decide which path to go with getting HDs, but I tried to go with something that would give me the most "bang for my buck" -- those Terabyte HDs are still EXPENSIVE, and so is the Raptor 150GB...
I figured that two additional hard drives (in addition to the stock 1 pre-installed) would be the best way to go, to give me three. I ended up deciding on two Western Digital 500GB drives, for about $94 each, not a bad deal.
I plan to run my Leopard OS and system on one, install Tiger on another as backup, and use this one for media files, video, downloads, and music...projects, etc...
Then use the other one for Windows XP -- partition and use half as a bootcamp 250GB drive, install games and Windows programs on that...then use the other partition for Parallels and Fusion Hard Drive images, and other miscellaneous backup...
TOTAL - 1.35TB of hard disk space, 3 drives, less than $200 to add them. Not bad.