May I remind you people that I7 only works with DDR3 RAM, thus both his orignal and samuraid's would not work on an I7.
Nvidia cards are graphically weaker than ATI's top so go ATI for graphics. Nvidia's top cars however have additional processor support and so reduce load from your CPU and run it on the graphic card. Thus for model rendering top range nvidia cards might (not sure) be faster than ATI ones as they tend to be processor rendered as apposed to graphic processor. I however like nvidia as they seem to work well, so it is up to you which to go.
I would much rather go with 4 GB DDR3 than 8 GB DDR2, as then I would future proof the PC for an I7, if not even get one.
Most modern games load the graphic card far more than the processor, thus for gamming it is recommendable to get a better graphic card than processor. Only excpetion I know are RTS games like supreme commanders. Basically, ingame you would notice hardly any preformance change from a slower CPU and a faster one but you will easilly notice the difference between a faster GPU.
In the end, an I7 or quad core like you have choosen will run almost every modern game under normal conditions with hardly any noticable difference, thus spending the money on a better graphic card would yield far better FPS or graphic quality.
I7 would make a big difference with model rendering if it uses the CPU, as those usually take great advantage of threading and the I7's improved threading capabilities would yield the most then. But games I do not believe will not use its 8 thread capabilities much better than 4 threads and until the CPU becomes the limating factor, it would seem pointless to get an excessive one.
EDIT - Just noticed his one list which includeds I7 and DDR3 ram, DOH:
It better work.
