I personally would go quad. Some developers say they will skip dual core and go straight to quad soon. Quad is more versatile if you do lots of a/v like photoshop, encoding etc besides gaming. Also gaming is usually more gfx limited than cpu unless you’re running crazy resolutions. I cant tell 80 fps from 89 fps. However, dual’s run cooler and usually have higher mhz.
As for graphics card, the 8800GTS 320mb IS the best bang for the buck. Nothing can touch it for the money. The extra 320mb on the higher model doenst do much unless at high resolutions.
If you dont overclock, the cheapest RAM you can get is 1GB 667mhz HP for $25 after rebate. Sometimes even cheaper. I got it for $15.
I would get the one of the P35 boards with DDR2. DDR3 is crazy expensive and the chipset seems to give a better boost than new DDR3.
Finally, for power supply. Go get a Corsair 620watt from Buy.com. You will not regret it.