OTL are they? I would stay with the high power; the 4's thrive on it. Seriously I have tried lots of amps on these and the big SS powerhouse names like Threshold work best but I have a sleeper amp that we stumbled upon during a tryout. If you can't find a used class A SS amp. The Audio Research D-120b. SS and pretty cheap around 600$ or less used. Talk about the perception of power: this is it. Very massive sounding. Tube wise; the best was the Harmon Kardon Citation II. In fact we are listening to that combination now, my friend has it here for storage since he's moving. 60 watts per side but huge transformers. Still; I personally like the 50 watt Threshold myself. The Class A runs hot but the sound is much more musical. Wayne has most definately voiced these for big SS watts; not that they don't work with tubes but they like SS. This of course is all my opinion and to be taken with a grain of your personal salt. I only offer that I love these speakers and have tried many of my acquaintences amps on them. They do rise to the level of the equipment, don't be tempted to sell them short with cheap amps; you will regret it. Sorry if this is irrelevent to your question.