So, what I think you may be hearing ... there are a number of youtube videos, with the head of Zu Audio, as well as the reviewer, Corey Greenberg, where they talk about amps that match up well with Zu speakers. I believe that they were referencing the Omens and the Dirty Weekenders. Both were saying that the older integrated amps and receivers do very well with the Zu speakers. In fact the reference was to try an old receiver that you may have in the attic. Corey was also talking about pairing them with the NAD 316 BEE.
I took delivery on a pair of Zu Dirty Weekenders about a month ago and I am having a blast with them. So far, they are sounding better with my tube amp (Prima Luna Prologue 5) fronted with a Musical Fidelity CD PRE 24 than with other solid state amps that I own. Even my wife commented the other day how much she liked music played out of the Dirty Weekenders ... much more alive. She rarely comments on anything other than speaker cabinet finishes and how much stuff I have around.
I would stay put with the Yamaha, at least as long as I was holding on to the Omens.
Rich