A 15 watt tube amp is not going to work with the Gershmans. I've heard 30 and 40 watt tubes with the Gershman Avantgarde, and they don't work either. They can't control that "mass loaded" woofer with the ring on it.
At lower volumes, you're okay, but if the music has a lot of deep bass in it or if you have to play loud, that woofer flops around like crazy, exaggerating and muddying the bass.
At lower volumes, you're okay, but if the music has a lot of deep bass in it or if you have to play loud, that woofer flops around like crazy, exaggerating and muddying the bass.