I have Duets in my primary system and a Tempo in my secondary. The Duets are not going anywhere. They drive Harbeth 40.2's. I am 100% satisfied with them. They are a step up from the Tempo, but not a HUGE step (family resemblance).
Whether the Duets have all the bass "heft" of heavy-iron class AB power amps--think Accuphase, Coda, or your Gryphon--I couldn't say. You'd need to do a side by side to be sure. I'm not sure if Alberto Guerra does home trials. He is, BTW, a pleasure to deal with.

