Kaiju,

Perhaps as important as "class" of amp is whether the amp has 4 ohm taps. And, truth be told, sometimes impedance dips can seem worse than they are. For instance, upstairs I'm running tube amps with speaks (Merlins) with impedance dips down to about 3 ohms (don't know the phase angle). So I initially tried the 4 ohm taps on my tube amps (Manley Neo-Classic 300B and Granite Audio 864 SR [KT-88]). But, in operation, gain, soundstage, the whole presentation seemed "shrunken," less potent and, well, not as satisfying as usual. So I switched back to the 8 ohm taps and, voila! The presentation was significantly superior in every way. Additionally, in feeling the transformers after an hour of operation they were no warmer than usual. Thus, suggesting, again, that you just have to try each variable in a system, even those counter-intuitive or seemingly contra-indicated, to determine what works for your system. Final example, downstairs (M3 Sapphires) I'm running 50 watt class A 845 monos off their 4 ohm taps and the system sounds F'ing splendiforous. Can't ascertain any difference between the 4 ohm and 8 ohm taps so I run with 4 ohms to ease the amps' load. It's all magic.