Setup: Boss GT-8 multieffect -> Engl e530 preamp -> fx return of Boss GT-8 -> GPA-100 poweramp
I actually didn't buy this for the power amp capability, but rather for it's EQ. I've previously used my Engl preamp's built-in poweramp (2x1,5w solidstate) and it has been loud enough for bedroom playing, but it sounds extremely dull on its own in my setup. I've corrected this with alot of EQing on my multieffect, but it required alot of boosting on high end, which left the tone kinda unnatural and at times digitally distorting, not to mention having to menu dive to tweak, which I found myself more than actually playing. After getting the GPA-100, I'm getting almost all of the EQing with just the preamp and GPA, with some fine tuning on the the GT-8. Now I'm very happy with my tone, and if it needs tweaking, I just turn a knob rather than go thru menus. Also theres lot more clarity in the sound, likely more headroom from higher wattage. The EQ knobs have pretty wide range and the volume feels nice to use.
The neutral position notch on the EQ knobs isn't exactly at 12 o'clock as some have mentioned, but this is a minor issue and doesn't affect operation. A presence knob and a DI out like on Power stage 200 or Kyro Duo would have been nice, but comparing the prices I can't really complain.
Overall I think this is a good product (this is after 1,5 weeks tho) for a bedroom musician with preamps or modeller. I don't know how loud it gets, but I feel it might not work for all band situations. It's not quite as versatile as other pedalboard amps, but at less than 3rd of the price of next competitor, it's well worth it if you can get the other features by other means.