Thanks for the speedy and thorough reply, TheRealDrew!
No problem 
I'll probably be shooting with a Sony HDV camcorder so I don't know if that's considered full uncompressed HD or not.
HDV is not full unccompressed HD, I even edited in on the old Powerbook so you should be fine. Converting to some other formats will take up more room, but are easier to work with (AIC and ProRez). HDV itself will take up about 13 Gigs per hour.
I assumed loading up on the RAM would be important and aftermarket is probably the better bet. How much RAM would you recommend to run things effectively. The basic Mac Tower comes with 2GB.
Again the more the merrier, though applications do not necessarily use all of it (though hopefully future versions may.) I think Final Cut maxes out at 4 Gigs and Photoshop has some limits. I threw an extra 8 in for a total of 10. Will help if you have more than one application running. The 4 Gig chips are still kind of pricey, the 2 gig chips seemed to give the most bang for the buck.
http://eshop.macsales.com/shop/memory/Mac-Pro-Memory
I'm not really familiar with the file sizes for HDV either. Do you really need 4 terrabytes or are you storing large amounts of video and data. I generally will shoot/capture 4 to 6 hours of video from a set of dives and edit it into one video around an hour long or so.
I just got a ton of files
13 Gigs an hour for HDV. With drives so inexpensive even if you use AIC or ProRes you can still get enough space for a relative song. Remeber though the best move is not to have your scratch disk or media on the same drive as the OS and Application. Real easy though to do either internally or externally.
I'm a little confused on the RAID card though. Is that to support external drives only? Will I need more external drive space or will mulitple internal drives suffice? I guess I'm wondering how much harddrive space I will need for everything and then choosing if they should be internal or external.
THe RAID card Apple offers is for the internal drives. There are other cards for external drives and/or external hardware RAIDs that are also fine. I order the internal one just because and I am not sure I would tell someone to get it. I just wanted some felxibilty on a hardware side of things internally, but really not needed I guess. It was just easier for me to order at the time and Apple to install so I did not have to think about it. With 4 internal bays and 750 Gig drives so inexpensive you could start with that. Have one of the drives as the media holder, the second that you back up the media to and the 3rd as the scratch/render and for what you are looking at doing you will be golden. The 750 Gig will hold 50+ hours of HDV.
The 8800 video card is a $150 option with the base tower package. Seems like a cheap enough upgrade for video.
That was my thinking though the card is not fully (yet) what it is cracked up to be. Tests well on gaming, but not as well as it otherwise should for what it is being mentioned for. On the other hand hopefully things will catch up. Everything seems to indicate it is a driver issue, but I am not sure.
http://www.barefeats.com/york2.html there was also another less flattering benchmark on the site but could not put my hands on it right now.
Personaly I would still get the card, but may have passed on the RAID card since I have alot of external items also. Me just being lazy and having some (a bit false) sense of security under RAID 5. For the most part my main footage is off the Tower and on externals, I use the internals for other things, some renders and so forth.