David Berning Siegfried 300b: Simply amazing resolution, transparency, and dynamics. Never heard better along these metrics. No congestion with classical music. I also didn't think the amp was lean in any way. However, the amp is no longer made and my friend won't sell mine back to me. I regret getting rid of this amp. I would highly recommend this one for the Duos. I think it would suit your purposes perfectly.
Kronzilla SM: Full bodied and good timbre. This is my current amp. It's a decidedly warmer sound than the Berning. Also not as forward. The soundstage emanates from behind the speakers but is coherent and stable. I don't like the fact that it emanates from behind the speakers but others do. All-in-all a great choice if you like a warm, full-bodied sound. Again everything is relative. It's a neutral amp but is on the side of warm and full-bodied but not to a fault.
Viva Sentesi: Similar to Kronzilla but not as resolving and the top end seemed rolled. Everything else was good though, especially at the price point.
Hope this helps. Someone I know uses the Kondo Neiro's with great results (not surprising).
Kronzilla SM: Full bodied and good timbre. This is my current amp. It's a decidedly warmer sound than the Berning. Also not as forward. The soundstage emanates from behind the speakers but is coherent and stable. I don't like the fact that it emanates from behind the speakers but others do. All-in-all a great choice if you like a warm, full-bodied sound. Again everything is relative. It's a neutral amp but is on the side of warm and full-bodied but not to a fault.
Viva Sentesi: Similar to Kronzilla but not as resolving and the top end seemed rolled. Everything else was good though, especially at the price point.
Hope this helps. Someone I know uses the Kondo Neiro's with great results (not surprising).