Bi-amping Infinity Quantum 2 - mid/high amp


When (IF?) I finish rebulding the crossovers of my Quantum 2, I want to (passive) bi-amp. 

Sturdy (under 2 Ohm!) power for the bass (class A/B, Adcom 545?). 

I would like to use a tube amp for mid/high, but not sure how much power the low/mid needs (may be outside of 'tube power' range)? Not ready for tri amping. 

Alternative class A?

kraftwerkturbo