Taxer.....NEgative connotation to that moniker, right? (;^)...
The best MV amps Fender has ever built would be the Super Champ, Princeton REverb II and Deluxe REverb II from the Rivera/Jahns era of 1982-1985. Handwired little amps that do BF REverb amp coutnry and surf tones very well, Tweed tones well, adn go into high gain territory well. Fender has never come close to doing it so well as they did in these amps, ime. Noone has ever built a handwired amp like this for the price that one can buy one at.
FWIW, I like power tube involvement both in clean modes and OD. Harmonics start jumping with power tubes working. Running MV's down low, one is dealing with preamp gain solely. Nothing wrong with that if that is what one wants. but using a lower wattage amp that can be pushed in the output section when going for OD yields a fuller and richer sound, imho, than does running high preamp gain with power tubes barely involved.
So, I sort of ageree with dickysofa's statement "but amps like the AC30 and Twin are supposed to be turned up and the tubes driven.".... I would say taht ALL amps need to be run at a level that brings the power tubes into true action. THerefore, use small amps for small venues. USe larger amps..or mic little amps...for larger venues. Get those power tubes working, imho. Preamp OD is great, but when you add to that soem power tubes pushing in to OD, you get that big soudn...at whatever level that particular amp can muster, right?