Need a heavy duty receptacle

Get one of those 3" angle type "L" brackets.
Mount it above your outlet to the stud. Then attach a cable tie to your power cord from the "L" bracket.

Interesting mention about installing the outlet with the ground up. Curious about how that "holds" better?

With the ground facing up there is a greater mechanical downward motion resistance of the ground pin of the male plug than there is with the ground facing down.

Mechanically the ground pin resists downward pressure from the weight of the PC more than it will with the ground facing down.

In the case of a straight out pulling motion, tension pressure resistance, there is no difference.
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When is somebody going to come up with a "twist lock" power cord and receptacle for us crazy audio people. You know like they use for pools.

There are "twist lock" outlets and plugs ranging from 15amps on up to 240v 60amp for appliances. A good electrical supply will carry a selection. I used 3-20amp "twist locks" to power my rack of gear. I have them floor mounted, It weighs about 400lbs and doesn't get moved often, but I sure don't want them coming out without my knowing . . .

Porter Ports are installed, but have to report that they don't hold the power cords any better than the outlets I replaced. I did manage to "form" the power cords (they are stiff!) so that they are resting on the floor, which now picks up most of the weight of them. It'll work unless someone hits one with the vacuum.
Don't get me wrong, the Porter Ports are far superior in quality than the cheap outlets I replaced, and I probably would have replaced them anyway.

Jonoulman,
I'm aware of the twist lock plugs and outlets in the electrical supply stores. I would imagine you had to make a DIY power cord?