Good post Oregonpapa..
Agree the new REF amps sure packs power and that they'll drive almost any speakers sufficiently. However much also depending on the room size, how loud you normally listen to, and the types of music.
When mood kicks in, I'd sometime like to blast my system a little and feel that excitement of room being pressurized--the REF150 just barely made it. Of course I'm talking dB levels where you actually feel waves of air surrounding body--loud. Thus got me thinking during those moments of the REF250.. Not that I need them, but sometimes good to have reserve watts up the sleeve. I'll stick with my REF150 for now as a single stereo chassis is preferable in my set-up. So far they've been performing flawlessly and I'm just about to pass the 500 hour mark--once settled, it's a great amp!
So just a little heed of caution there to better try the REF75 out first in your home/system prior when possible to see that they'll not only drive your speakers, but drive them with aplomb. In another system I'm familiar with, driving Sashas in a 4x5m room, the REF150 seems to have ample reserves. My speakers are slightly easier load, but in a bigger room.