Depends how loud you want to listen , I think. I've got a 0.9W 12B4 amp w/o preamp running into my 2Pi Towers. For my bedroom setup it sounds great and goes plenty loud for me. Course, it's nothing like running my 50W NAD amp into them, but I don't notice a difference at the levels the 12B4 runs if the NAD volume is set the same. In fact, the 12B4 sounds much better, even in the bass dept. To each his own I guess.