I agree that the Mac Pro is simply too much money if you are not into a few very specific applications.

But. Have you considered an iMac?

No, no, I'm serious. I used to use nothing but towers, but sooner or later I realized I wasn't upgrading them nearly as often as I told myself I would, and that what I really wanted was a computer that was quiet, compact, and moderately powerful, if not bleeding edge. I bought a 24" iMac with an upgraded graphics card, and it's been about two years, but it still works great. I've been playing a lot of the Orange Box and Bioshock on the Windows side, and Civ 4 on the Mac side. Games run great in both OSes, and of course I use the Mac OS for pretty much everything else.

I'm not saying it's necessarily the best choice for you, but I am saying you should consider it. Check out their website: http://store.apple.com/us/browse/home/shop_mac/family/imac?mco=MTE3MDM and pay special attention to the 24" model. You can go in and upgrade to a GeForce 8800 w/ 512MB for an extra $150. That means for $1,949 you are getting a 24" 1900 x 1200 monitor, and a rather powerful gaming computer. Also, $169 for a three year warranty isn't bad at all.