Shaun, I have my M5 bookshelves 13.5 feet apart in my living room. I am sitting 12 feet away on the diagonal. With a Chromecast Audio feeding them through a 1000, I am hitting 103.5dBC peaks. The 1000 can't do no more through that Chromecast. The soundstage is huge, instrument position is easily discernible, it is clean, it is non-fatiguing and the bass is well-controlled and full - no sub required. I know with the 1500 feeding them, they could hit 107dBC peaks cleanly. They will go higher but then I can hear woofer distortion and depending on the song, mid-woofer distortion.
For reference, on my main system, the M100/800v4/1500/firestick/Onk can hit 108.5dBC peaks at 12 feet away on the same tune when the Onk is set to 0 (reference). The system can be driven to peaks of 110 clean dB and as high as 112 with some acceptable distortion from the HP drivers. At 110 it becomes painful.
A really nice rocking level on my main system is -5 on the Onk. That delivers 104dBC peaks in 2.1. That level doesnt apply to all songs. Some I have to turn up to +12 and that delivers an incredible and immensely overwhelming performance!