What is your monitor resolution and what games are you trying to play?
GTX 660 is a great card and the A8-3850 isn't that slow. I don't see why would couldn't handle a nice card with that system, even if you won't be getting i5-3570 performance.
I don't have any specific game in mind, maybe GW2 and Skyrim, but I just wanted to upgrade to something that fit well.
I ended up being a mix match system based on things I had and able to get easily enough.
The monitor will be 1920 x 1080, last upgrade after GPU, but right now its 1440x900.