At idle, the +12v bounced back and forth between 12.0 and 11.98, spending most of its time at 12.0. I launched Sandra Processor Arithmetic Benchmark, which maxes out the CPU. The +12v bounced between 11.97 and 11.95, very tolerable with a multiple railed CPU of this wattage.
Next, while running Sandra, I launched Ozone3D's FurMark. FurMark is an OpenGL benchmark that checks out the GPU with a moving furry doughnut. It will put a 100% load on the GPU, which further stresses the PSU.
Adding FurMark to the mix with the HD 4550 didn't phase the Potency 550 a bit, I again saw the same flutter between 11.97 and 11.95. Time to change video cards.
Next I decided on a logical CrossFire setup that you might use the Tuniq Potency 550 with, a Radeon HD 4670 and a Radeon HD 4650. These are both “mainstream” cards, which basically mean that they cost less than $100. A logical SLI setup would be a pair of geForce 9550 video cards.
The Potency 550 did drop a little more with the pair of cards, while both CPU and GPUs were under load, the +12v bounced between 11.93v and 11.95v. Still well within the standard, but definitely pushing the reasonable limits of the PSU.
Finally, I used a “real” video card, a Radeon HD 4850. This isn't a power hungry card, but I really didn't know how the Potency 550 would perform with a true gaming card.
The meter bounced around a lot while the programs were launching, but once both programs were running, the +12v bounced back and forth between 11.93 and 11.94. With both the CPU and GPU maxed, I experienced only a .07v drop in voltage.