Well, lets hope there's no bottlenecks in your system. Might as well post your rig too while you're at it :-P Well, 22 inches of gaming, you have two choices, basically:
Force3D HD4870 512MB @ R2416
or
Inno3D GeForce GTX260 CORE216 @ R2260
Do yourself a favour, take the GTX260. Its the 216-core version, its faster than the HD4870, its got more memory than the HD4870, and its cheaper. Plus, it comes with Company of Heroes: Opposing Force and Ghost Recon Advanced Warfighter 2. Epic win-win situation, I think you'll agree.