@EraserXIV: The `problem` is your CPU, it cannot feed the graphics card with enough data for it to run at full speed.
Your PSU is fine, if it were not so, at the worst your system would not boot, at least, it would be unstable with random crashes/lockups/uncommanded reboots.
All is not lost, though, graphic cards do AA/AF on chip, so you can turn both up without sacrificing frames (as Rangers said).
AS for MB/CPU/RAM upgrades...Why not check out our other friendly and helpful forums?;)
Exactly. To test the bottleneck, try to go to 8xAA and 16xAF and see what the difference is in FPS from 0xAA and 0xAF. It shouldn't be too much different.