(1) Get as many cores as you can afford

(2) I hardly ever hit the wall on ram (16Gig ) but 24 would be safe

(3)  good video card with at least a gig of ram 2 would be a lot better for large scenes.

(4) Go for a bigger power supply at least 850 or bigger as hardware is taking more and more power

(5) last but not least get a big case so your parts have plenty of room to cool off and lots of low speed fans

(6) really last this time, a couple gig hard drive or two 1 gig and set up a raid for faster read write, preferably 7200 so they are not so loud.

Then print an alien ware sticker and staple it to the side of your case so the gamers are impressed. :-)

Tom