I own the M3 Sapphires and use them in a 13X20X6.5’ dedicated basement listening room. I used to use two subs with my previous speakers (towers, bookshelf, Maggies) but moved them out when I got the Spatials. I use a 30W Class A amp (Pass Labs XA30.5) and I’ve never seen it leave Class A. I listen at 80 db avg. with 85db peaks (A Weighted). Lots of good comments on pairing the Spatials with LTA tube amps.
I love the dynamics of the Spatials and don’t feel they are missing any slam, nor do they overload the room! Honestly, they are amazingly refined speakers. The detail and texture in the bass is extraordinary. I have no Klipsch experience but I suspect they are VERY different in their presentation.