well i would say this...yes wait until the prices go down. but i'd say don't upgrade the processor. just get the 7900 GT or maybe 7600GT if you'd rather but then in a year when you get a better system take the 7900GT out and put it into the other one.
sure there will be a better video card out then but a 7900GT will last you for quite a while. and you'd have that completely outa the way. maybe upgrade ram too.
basically i'm saying just get parts that you'll be able to take back out and put into a 939, 940 or AMD2 socket motherboard...(754's are falling behind in technology and you probably won't end up getting one).
IF you upgrade the processor it's unlikely you'll be able to use it in a newer rig. that's my advise. just upgrade anything but the processor...it's not a bad one anyways...just not as fast as the new ones.
Antec NeoPower 650W
Intel Core 2 Duo E8400 (w/ Arctic Freezer 7)
4GB DDR2-1000 G.Skill
Sapphire x1950 Pro 512mb (w/ V700)
250GB, 500GB and 1.5TB Seagate Barracudas (2.25TB total)
Fatal1ty XtremeGamer sound card *** generic TV tuner
Xclio 3060 case *** HannsG 22" monitor
XP Pro / Ubuntu 7.10 *** Razer Copperhead and Tarantula