This is the first build:
amd 6400 x2 black edition
Asus m2n32 sli deluxe wireless
WD Caviar 280 gig (from old comp an HP a1520n)
XFX 7900 GT
lightscribe dvd/cd writer (also from the a1520n)
Antec Smartpower 500W PSU
Blue Orb II for cooling
Soundblaster card (to fix stability issues with the onboard sound on this board)
twin 2x 1gig corsair c4dhx
Vista Ultimate 64 bit
Soooo next step is: what?
To speed up games should I:
Raid with 2 barracuda 7200.11 320gig HDD's
Purchase an PNY XLR8 GeForce 9800 GTX 512MB
get more memory?
The 9800GTX will give you the biggest increase in gaming performance, but all of your choices will cost you drastically different amounts of money... You could get the HDD's and memory and still spend less than the 9800GTX.
For the price of the 9800GTX, I think a better choice would be to get an 8800GTS (G92) and another 2 gigs of ram.