the agp version of the 6800Gt is much cheaper then PCIe. i would honestly do this (follow these instructions to the letter
THIS IS GIGABYTES NEW NFORCE4 for only 129! PCIe!
AMD 3500+ with NewCastle Core and 939 PIN!! Only 272!!
RAM: this stuff is the most important! This is some of the best RAM on the market, GEIL ownz!
And once again, that Video Card: This is not on NEWEGG, so pls don't ask.
Ok , build this all together, and you will have a bad ass PC under whatever tower you choose. Just make sure you have at least a 475watt PS, because the 6800GT is a power hog, and the 3500+ isnt exactly power saving either....