Solid State watts to power Zu Defintions?

Let's see: very efficient speakers, nice pre amp, and you need a good amp?
Have you considered a Burson?
I have the integrated version for my Tonians (not as efficient as yours-the Tonians are 95db) and it sounds wonderful. I believe the amp is around 90 watts per channel, class AB, and it has the cleanest sound in my limited experience. Not antiseptic or analytical but clean, rich, full, and engaging with detail aplenty and not at the expense of tone, body and texture. Great for all kinds of music.

There is a dealer local to me who used to carry Zu and had a pair of the original Definitions driven by a Sim Audio Moon W-8 power amp, and they sounded fantastic. Having said that, when they switched over to a top of the line VTL tube amp/pre combo, it sounded even better.

WarrenH---check out a used Mac 402 (with quad balanced circuit). they are really cheap now that the 452 came out. and with Mac, easy to resell of course.

McIntosh solid state amps with both autoformer outputs and the quad-differential topology. As good as solid state will get on Defs. Pick your price; try for monoblocks; you're golden.

Phil

Love my Def 2's on the end of my Naim set up Cd 555; pre NAC 552; power NAP 300. perfect trans atlantic union.