Personally, I think the 8-core is slightly overkill for gaming. Most games don't even use more than 4 at a time.
In my opinion, you should go with the 6-core 6350 (or 6300, if you're confident in overclocking). The money you saved on the CPU could then be put towards the newer, more powerful Radeon R9 280X GPU.
EDIT: I meant the 285.
And regarding your Power Supply: Make sure it's a good one! Don't cheap out on the PSU. It's very important to get a good, reliable PSU. Because a Power Supply failure can destroy the rest of your PC, or worse, can cause a fire.
"Never argue with stupid people. They will drag you down to their level and then beat you with experience."
-Samuel Clemens