I was running a 30W (class A) tube amp when I upgraded my speakers to Martin Logan Spires.
While I could get sound out of them, I couldn't really make them sing. And no, my days of listening to rock-concert level sound pressure values are long behind me.
I first upgraded to a 205 W pro amp (Soundcraftsmen PCR800) which resulted in an incredible improvement over the tube amp. I've since upgraded to a pair of Soundcraftsmen monoblocks that are capable of 900 W at 4 Ohms.
Is 900 W complete overkill? The extra power isn't about playing my system loud - it's about better instrument separation and definition at low volumes.
While there are tube amps out there that can efficiently drive ML's, they tend to be in the upper price range.
I find that the best combo for ML's is a tube preamp, coupled with solid state monoblocks.
YMMV.