Bluex :
I think that the I7 4770k is slightly better but only by .1GHz so if I were you I would stay with the 3570k. If you need turbo-Boost then yes I would get the i7 4770k. The i5 3570k looks like a great CPU though!
If GHz was the only thing that mattered, AMD CPUs would completely dominate Intel CPUs. However, that is not the case.
To the OP, overclock your CPU. If you're looking to get a better GPU, go with a GOOD single GPU, as I recall 78xx AMD GPUs weren't too great in crossfire.
And overclocking is not hard, there are a vast number of guides throughout the internet that will detail step by step of what you need to do. Find one that suites you, or is the easiest to read for you, and follow it.