I was thinking about:

Intel Core 2 Duo E6600 (Would Athalon x2 be better?)
1 Gig of Ram (Easy to upgrade later)
2 x 7600GT 256 Graphics cards (Easy to upgrade later)
2 x 250 Gb Hard drives
Soundblaster SE 7.1 soundcard
550W PSU
2x DVD rewriters
Vista Home Premium
I dont think you should go with the dual graphics cards. I just got an Intel Core 2 Duo E6400 with 2 gig of ram a 7950gt512 graphics card, 600W PSU and built in soundblaster 7.1 and can play MTW online at max settings with no lag as long as all others have good pcs and connections. I think one really good graphics card is better than two good ones. Id stay away from the vista as well. I got my whole pc custom built for around 1100 bucks with all new name brand parts. Id go with the two gig of memory from the start.