Excellent PSU.
Only thing I can think of now is maybe you have something running in the background while playing your games.
I did a fresh format and reinstall of Windows. Only installed the drivers and games to test, and the problem persists. I don't think anything's running in the background, processes show 0-5% usage before I start the game up. Okay, so I've ruled out RAM (memtest86 showed no errors) GPU (swapped 970 with 560 and hiccups continued) and now PSU. Any tips on pinpointing whether it's the CPU or mobo?