When I demoed my D7s at his house he was using a Jadis I50 50WPC class A tube integrated that had more balls than a 1000 watt subwoofer.
Seriously, it drove them with dexterity and strength and the bass was out of this world- all the while retaining the sweet midrange and clear highs tube amps are known for- perfectly balancing the D7 tendencies.
The also sounded spell binding with my 100 WPC rogue audio cronus magnum ii and ultimately the Stereo 100.