I have a Core i5 750 clocked at 4GHz, Radeon 5850 1GB and 4GB of RAM. Same resolution as you; you have more CPU power (shouldn't be a factor) and about 20-25% more GPU power.
(Anand's Bench)
I play the game on the High preset at 1920x1080 and it's rock solid, even on 64-player Conquest maps (the High Preset uses post-processing FXAA). Enabling 4xx MSAA slows things down for me, that is where your increased GPU power should pick up the slack.
The Ultra Preset works mostly fine in Single-Player, in Multi-player causes very annoying slowdowns (unless you are on an empty server with no explosions and mayhem

). I'm guessing it
might work on Ultra but without 4x MSAA.
Either way, it doesn't matter. It looks pretty freaking fantastic on High and after the first hour or so, you will get over the fact that you can't max out the game engine. I haven't even bothered trying to tweak the graphics by switching the graphic options to Ultra one-by-one and checking which feature breaks the camel's back. Who's got time when there are noobs to pwn?