not to mention you can do all sorts of things on a pc
x box 360 uses the R500 core, whereas the X1900XTX uses the R580. so no competition, the xbox wil get owned by that system.
o btw, you dont need a crossfire card for one single card unless u plan on upgrading to two cards in the future which i highly not recommend you coz you need to wait for the new directX 10 cards
Intel Core 2 Duo E6420 Conroe 2.13ghz
Gigabyte P35-S3 Motherboard
A-DATA 2x1GB DDR2 800mhz memory
Geforce 8600GT 256MB GDDR3 PCI-Express