I would say you can play a game like Crysis 2 @ 1080p with the graphics set to "Gamer" (lowest setting, but still looks good) and get decent performance. However, if you should install the DX11 patch for Crysis 2, then your card would struggle a bit.
You should also be able to play games like StarCraft 2.
Here's a review of the HD 6670 with benchmarks of some popular games. The games are mostly 1st person shooters, and are different from the types of games you like to play, but it will give you an idea how the HD 6670 ranks with other video cards in demanding games. Note that all graphic settings have been maxed out and the test rig uses an Intel Core i7-920 @ 3.8GHz.http://www.techpowerup.com/reviews/Powercolor/HD_6670/