You obviously mean the AMD Athlon X2 370K. AMD uses the "II" designation for its older K10 processors.
Well, yes... good enough if you don't mind a dual core. On games that can use more than 2 cores, you may bottle neck the GTX 650ti a bit. The 4GHZ speed will help, though. Can you step up to the Athlon X4 750K? Or 760K?
If all else is equal, yes. But you are comparing a fast dual core to a nearly as fast quad core. And today's games are becoming 4, 6, and even 8 core aware. If the game only uses 1 or 2 cores, then the dual core will be faster. But as the game uses more cores, that will out pace the GHZ difference.