I had the same question and this setup is almost identical to the one I'm building (same CPU and mobo, anyway)... I was going to go with 4x4GB but a friend told me that filling all 4 slots can degrade performance and 8GB is enough for gaming. Would you agree?
I'm going to update my build wishlist with one of these kits
based on this new information.
You really should have started a new thread.
Using all 4 slots for 16GB will not degrade anything but 8GB is fine for gaming. To be honest you see only a little gain in going from 4GB to 8GB if it is just for gaming. Some newer games do better with 8GB though. And DDR3 is dirt cheap.
The orignal poster was building for Photoshop as well as gaming. In their case it makes sense to go with 16GB because with Photoshop or any kind of video rendering you can not have too much memory.