I agree with Gonzo regarding the SSD Windows & gaming drive. It makes a huge difference.

I'm not familiar with AMD CPUs, so I'll let someone else deal with that. The I5 processors are very good for gaming, but I can buy the 4670k processor for $10 more than the 3570k here, and the Haswell should handle graphics better. I would definitely price compare the Haswell v/s the Ivey before buying.

If you just want to replace the GPU, you should be able to find some good deals now or soon, since AMDs announcement on Wednesday. Their 7950 were a good deal already, and lately I've seen them dipping under $200 with MIR.

Make sure you check your ISP. Some people were having issues with throttling by their providers.