While not a powerhouse, that card is OK for low res, it's really going to be the CPU that will limit your gaming experience. I have an old card (8600 GTS) that is a bit slower than the 4670, and it can still play Dragon Age at max settings at 1280x1024 just fine (didn't measure, but probably just a tad over 30-40 FPS), but the old CPU it is paired with is faster than yours.
Anyway, point being that your card is more acceptable than your processor (especially since your res is 1280x1024), so if you had to upgrade one now, prioritize the CPU first. You can always lessen details if your GPU starts to grow old on you. But if your CPU is the problem, there's no in-game setting that says "lower CPU utilization by disabling 50 percent of enemy AI".
Anyway, point being that your card is more acceptable than your processor (especially since your res is 1280x1024), so if you had to upgrade one now, prioritize the CPU first. You can always lessen details if your GPU starts to grow old on you. But if your CPU is the problem, there's no in-game setting that says "lower CPU utilization by disabling 50 percent of enemy AI".