Pass Labs X250.5. I have listened to them in my reference system and now at our lakehouse. I would say that Pass Labs does solid state right. Great heft, detail, imaging presence and clarity. Playing this amp thru a Doug Jessie modified ATC Air Tight ATC 3 tube preamp and his mod of a Cambridge 840 C CD player. Speakers are Audio Physic Virgo. Inteeconnects are Cullen Cable copper and the Speaker Cables are Gabriel (copper, silver, gold). The sound is captivating, sublime and has had me listening most of the afternoon since getting everything hooked up. The Pass Labs amp is just outstanding. This is coming from a tube lover.