Almandog in your current setup I would always look at keeping things simple therefore, a sweet midrange/treble stereo tube amp is preferred IMO. If your truly going to commit to a tube amp you really have to select an amplifer that will help bring synergy and sonics you truly want in the midrange/treble area. I agree, tube rolling will allow you to change the sonics for Legacy Audio 20/20 (nice speaker BTW).
I wonder how much you really gain with MONO amps in the midrange/treble in your current setup. Most great MONOS will cost a lot so look at price/performance ratio hence, stereo tube amp may be a better cost alternative. Tube rolling alone for my two MC275 run in mono...$800 plus to do it right.
The key here is the external crossover which has to deal with two different amplifiers and the potential gain mismatch. The independent output-level controls will have to balance the levels between the woofer and midrange/treble amplifiers.
