I just found a 2008 Mac Pro in my price range. Is this the one you were thinking of?:
Two 2.8GHz Quad-Core Intel Xeon E5462 Processors (8 cores)
Yep. Buy that machine, it'll be great for what you're doing. 🙂
(I have that exact one, and I'm typing on it now.)
(Although, no offense, given what I originally paid for it, I'm sad to see the price range it's entered. 😛 )