For graphics, you want more video RAM for higher resolutions. If you plan to play at 1080p, then you'll want at least 1GB DDR (which ~512-640 DDR2 or ~256-384 DDR3 effectively performs equally to) minimum.
Continue buying your parts online, but if you have computer parts stores locally, you can check them for the occasional deal that beats the online stores. Those don't happen often, but when they do, it's nice.
Most gaming graphics have to do with the CPU you have, the amount of system RAM you've got, the quality of the motherboard, and the GPU. Since your GPU is mostly top-notch, I'd expect you can play almost any game at full settings (especially if you're not playing online. If you play online, you'll experience a little more lag because your computer's got to worry about yet another aspect of the game). The only ones you won't be able to handle at the full settings are the overly graphics-intensive ones like Crysis.
Now, like I said, resolution mainly deals with your video RAM. If you can't do full resolution with the card you've got, just figure out what the next lowest res is at the same aspect ratio (or close to it), and downgrade, then you'll be fine, and you probably won't notice any significant difference. You can also go into your nVidia graphics software and probably designate more system RAM toward video memory (if you can't, then it's something you'll change in your BIOS). Since you're running DDR3 system memory, dedicating some of that to your video will probably get you set on that.
What motherboard is in your system? If it's a mid- to high-quality Gigabyte mobo (which Newegg loves), you'll probably already have 128MB DDR3 dedicated onboard video RAM. With that and the 256MB DDR2 on my video card, my graphics software is recognizing it as well over 1GB clocking at 900MHz. I have 8GB system memory, and I think I dedicated a full gig of that to my video as well, so with all of that together, the ATI Catalyst Control Center claims I have 3323MB video memory ahaha.
SW-5120-1900-6153
