I owned the Pass Labs X350.5. Reno HiFi sent me the X350.8 to try and I thought the X350.5 was livelier than the newer X350.8 version. So, I sent the X350.8 back.
At the same time, I also owned the Pass Labs X10 preamp. Again, not overwhelmed. But we all have different speakers, rooms, preferences etc.
ozzy