When hearing Brian’s U1PX’s driven by Atma-sphere MA-1’s, we never got into clipping level concerns. However, I never had him stress them or play at a level higher than he did, because I was happy with his chosen level and what I heard.
Brian also had the Atma-sphere MA-2’s on hand. They had a bit more gravitas (if you will), but besides that, essentially sounded the same as the MA-1’s. Again I didn’t do a how-loud-will-they-play comparison between the two amps, as higher volume levels weren’t warranted for my tastes. -Mike