Ya, i defently think you should get a amd athalon xp processor, the 2400 would be a nice buy, although i'm getting a 2500 complete with the new barton core and 512kb L2 cache.
According to what i know the Ti series cards arent completely direct x 9 supported, although starting with the ati radeon 9200 (both pro and non-pro) the radion series is. Direct X 9 is something that should be one of the first on the list when your getting a graphics cards, so correct me if i'm wrong but the TI wont complete support direct x 9. I agree, dont get a FX, DEFENTLY dont get a fx. Onboard sound on your nforce 2 bord should be very nice, yes, bu what about getting a Asus motherboard? they tend to do well in games as apposed to other boards. A valcano 9 fan and heatsink is a MUST, especially if your overclocking (remember, i'm talking about a amd athalon xp processor, dont get a pentium 4). I would get atleast a 400watt power supply. 512MB RAM should be sufficent, but remember to look at the motherboard your getting (whether it be a asus or anything else, although i recamend asus and so probably would other people) to see what type of RAM it takes, i heard pc 2700 should be the lowest type of DDR ram that a gamer should get at this time. Also one thing about the hard drive, A WESTERN DIGITAL! they totaly rock, especially get one with a 8MB cache.
And dont forget a kickass case to go along with all of it!
get a cheifet - dragon series from tigerdirect, right now their onsale with a $10 rebait and will only cost ya $49 before the rebait.
If you buy all the parts i've named and maybe other people will name too from www.pricewatch.com
and ww.tigerdiect.com , it shouldent cost you that much, although i dont know if your getting a monitor too.
i hope you totaly enjoy your new gaming pc when you build it or buy it or whatever. feel free to IM me if you wana talk about this more.