Small upgrade question

[Dark Shade]

I have a computer hooked up to my 65" DLP screen, and we often play games on it as well as watch movies (via DVI->HDMI cable). It has an Athlon 64 3000+ with 2GB of RAM and a GeForce 6800nu. I was wondering, without spending too much money, which AGP video card wouldn't make the CPU a bottleneck and save me some money? I assume one of these Radeon HD 3850's would bottleneck at the CPU for no extra benefit. All resolutions are running at 1768x992 in games and desktop apps. Any suggestions? Or should I even bother