There are "official" and "unofficial" RAM frequencies. You can run 2400MHz RAM on an eg. Z77 mobo + Ivy Bridge CPU just fine while it only advertises 1600MHz at most and you can do this for AMD too. The RAM you buy is certified to run at a rated speed, that's all, you basically overclock it if you run it above the advertised frequency by the CPU vendor, but it will be stable.
The problem with that theory is that the A10-6800K natively supports DDR3 2133. The ram speed makes a substantial difference in GPU performance. Especially when you disable thermal throttling/power saving, since those settings have a negative effect on gaming performance even at stock speed.