Harbeth 40.2 or Vandersteen Quatro CT

you have room for 5a , Kento and 7’s. See my Poverty Bay sound system pictures. Obviously Quattro are going to work well also. Your amp is fine, it’s not holding you back..much....

have fun on your journey

Dig Tinawiren.....

Both of my Vandy systems are in the virtual systems pages...

Yep, Treo CT and 7 mk2 with the Vandy amps. IF you do the home demo be sensitive to what is involved with placement, tuning of Quattro and move the Harbeth out of the room.

The advantage of the Quattro over the Treo is they play lower, flatter and cleaner than the Treo and the subwoofer level and Q are adjustable. Cleaner because of high passing your amp. I have the Treo in a Condo, would have got Quattro but trying to not get evicted, ha !!!! 
Yes I have heard Kento, really amazing w M5 amplifiers...

Love the Quattros, especially the CT. I am a Vandersteen addict w two pair. Harbeth makes a lovely speaker also and your amplifier will work splendid w either- Vandersteen powered bass will free up your amp and yes robust as it is you will get better sound.
have fun, enjoy the music and the journey 
jim