hehe
Well, okay first things first. It's a pretty damn decent gaming system right now.
I would suggest first of all, running everything at stock, and see if the problem still exists. That aside and based on what you've mentioned I would suspect high HDD/SSD usage. You have ample host processing/ram/GPU power to play anything without stutter. What res are you gaming at?
Monitor disk usage while gaming. Use HWMon and monitor your system at idle and load (gaming in this case) and take screenshots of both, so we can look the CPU/GPU temps, voltage, usage etc.