Running it from the 32-bit executable worked, now it runs around 35-40 FPS with 1600x900 res with 2x anti-aliasing on High. Huh, why did it perform so terrible with the 64-bit exe? Thanks for the help.
I think your GPU might still be underperforming. I have a XFX 5850 and get ~35-40fps at 1920x1080p with settings on high and AA at x4.
According to Toms, a 5850 at very high and 1920x1080 w/ 0 AA gets ~30fps, and with AAx8 gets ~27 fps. http://www.tomshardware.com/reviews/radeon-hd-5850,2433-6.html
See in GPU-Z if your card is running at max speed during games. Also, make sure you have the latest GPU drivers, no Nvidia drivers whatsoever.