You could always upgrade computer poower supply if you are into DIY windows machines.
Purepower is a definite improvement, much better coherency and separation, I have compared stock and purepower side by side and the difference was obvious.
IMO purepower should be a step above solutions that just feed power to the USB as it bypasses the AP2 internal regulator and feeds very clean power to where it matters most. In fact I tested the Vaunix (which is not linear supply like the AQVOX bit is switching) with the PP AP2 and found it did more harm than good in my setup (my computer PSU already has very low ripple). I might try a USB supply in the future but IMO purepower is pretty much optimal.
After more than a first impression in my system, the Vaunix "did no harm." but did not improve things as I originally reported.