What sort of upgrade from Rega Brio to go with my Dynaudio's X12?

I’d have to agree your Dyns would appreciate more power, but all amps sound different so it really depends on what improvements and sound characteristics you’re looking for beyond just more power.  Also, what’s your budget, and are you looking for new or used?  This critical additional info will get you much better recommendations here.

I started to hear the weakness under 60 watts/8ohms with my Dynaudio speakers. There are 100s of choices, depends on your budget. I have been very happy with vintage gear.

CRAP,CRAP,CRAP!DON’T buy into the need more power BS,UNLESS your running in a BIG room OR always listening VERY LOUD!!!
I’ve run Dyn’s for YEARS with lower power tubes & SS amps..Started with Audience 52>Audience 52SE>X14 & now X18’s...BEST ever was pure Class A SS @ 25wpc..Sugden or the new Musical Fidelity Class A will bring out the best of your speakers..

Better sound quality?  Simple send it to be upgraded.  That solves that problem.

Did not mention in my response that I used the Rega Brio (newer, half sized form) for several years and was never enthralled with it.  I chalked it up to the speakers that I was using (Omega single drivers), which tend to do better with tubes.  Swapping in Ascend Acoustics didn't help matters.  I just found the sound to be very flat.  Suggesting it may be the amp, knowing nothing about the Dyns.