I'm driving mine with 12wpc SET monoblocks (845 output tubes) with never a hint of strain. Humongous transformers, though. I have the Gallo subwoofer amp to drive the woofers' second voice coils, so there's no shortage of bass. The Gallos obviously have a very benign impedance curve (8 ohms nominal). This is in an 18 x 40' room, BTW. Dave