I have to choose between these CPUs and I wanna play games. 6300 for 95€ and 3470 for 157€. I heard that the steamroller will be better than current FX in single threaded apps, is it true and what about the power consumption?
The i5 3470 performs better in games. Its the FX-8300 that matches the i5s in performance. But if you are on a budget, the FX-6300 is a fine CPU too. Enough to game with one graphics card without bottlenecking. The power consumption of the i5 is less. Ivy Bridge CPUs are generally very efficient.
It might be true that Steamroller will be better, or not. You should not worry too much about single threaded performance. The single threaded performance of the Piledriver architecture was behind what Intel has to offer. Being better might just mean catching up with Intel.