Bryston 135 Cubed

The Bryston B-135 Cubed is essentially a BP-17 Cubed plus a 2.5B3. Speaking as someone who has the BP-17 Cubed and 2.5B3 here, I would say it's hard to go wrong with the B-135 Cubed as an integrated amplifier provided Bryston's Cubed line in general provides the sound character you are looking for, and provided the 2.5B3 has enough drive capacity for your intended speaker.

I don't have that but do have a 4B3, which has similar circuitry for the power-amp part. It's a wonderful amp, to my ears in the same league as Classe, Pass Labs, and similar brands (though sounding a little different to me). I bought it after auditioning those two brands and several others, as well as the 4B3.