So it's come down to this. AverLAB is kaput. After waiting years for them to get their software together, they never came up with two-tone tests, multi-tone tests, nor fixed some serious bugs for raw data collection. It's still a great analyzer, but it's becoming less and less useful: too long to set up, clunky UI, slow FFT calculations, needs external HV probes to measure amps, can't do potentiometer matching, etc. The question is between APx525 or APx555. Or maybe their new measurement software that works with RME's USB thingy. Yes, AP now sells their software. I'm tending toward the real AP hardware units because the inputs can take HV for amps. This would be a massive time saver in addition to offering better measurements. I'm kind of tending toward the APx555 - mainly because the analog generator is insanely good. With digital measurements (DACs), the results are close enough, a few db off. However with amp measurements, the APx555 SINAD results are a good 7db better around 0.5Vrms. Even more than importantly than this is that the distortion patterns with the APx525 showing a bit more second order. Finally, the FFT processing speed is amazeballs and the UI of the AP is spectacular. At first I was scared of the interface because so many options are laid-out - but after 60 seconds, it all totally makes sense. I don't know if I want to get the APx555 because it seems like e-peening. Then again, I am gravely concerned about the misuse of measurements considering how easily they can be borked, and feel that the only one around to offer "legitimate" peer review of the guy with the APx555 would be me. This would be my own money, from my savings, and from the ads and sponsors paying for this. The Patreon still goes to loaners, shipping costs, site operations, etc.