I am an owner of Usher D2 equipped with the TAD 4001 driver. After few years of auditioning I can admit that these speakers can play amazingly well, especially with very good amplifiers. They can be partnered with tube monoblocks (Audion, 10W S.E 300B or Geroukis, 70W Parallel S.E amps 211 VT-4C) or solid state (Plinius 2 X 250W). Depending on what you want you can adapt the sound to your taste. Remember that although huge and heavy speakers (236 kg) they can sing even in small rooms.