Re: First Comp build!
For that budget, and that size of screen you will want at least an 8800GTS 320mb for that build.
Also, im pretty sure the Seagate 750GB drives are faster at the moment.
Lastly, unless you intent on going AMD, an intel build would be better. They overclock better, and they are newer technology. If you are willing to go intel i would suggest either a Q6600, or an E6750, or a cheaper E6550. And for the motherboard a Gigabyte P35-DS3R, or an ASUS P5K Delux (but only for the quad).
If you realy cant afford an expensive gpu, i would suggest a 1950XT or a 7900GS instead.