If we were local I'd do it. Last time I used it, it was to check the head unit and a new amp. I use it to check for distortion, then set my amps to the actual wattage I want by AC voltage. Personally, I think they are more useful for head units than amps, (my last two kenwood head units, both made the full voltage at 34, and then had a 10% bump at the max 35 (where it's distorting).
The last amp I used it on was my alpine PDX-F6 which is rated 150w x4 @ 4ohm-<0.005% THD+N @ 1W, <0.05% THD+N @ rated power. It started distorting (the DD1 registers at 1% THD), so I thought I would use my multimeter to check the output. It was pushing out 440w per x4 @4ohm before distorting. That definitely would have blown my components, which I was only planning on 120w x 4.
I think at this point, I could just sell it since I just finished what is hopefully my last change to my daily build. They work and they are good, but are you looking for max output before distortion or do you have a target wattage you want to be at?