Ayre Acoustics AX-5 Twenty

Who knows! It may sound like a $50,000 amp.  It’s been my experience that at a certain level there is less of a correlation of price to sound quality.  

You should listen to as many amps as you can and if possible, work with a dealer that can let you do an in-home audition. 

That's very difficult to say. Dynaudios typically demo with Octave gear, so no doubt there's great synergy there. I heard the C20s with Primaluna, which also sounded great.  As for Ayre, if their entry level preamp is this good (K5xeMP), then I'd be highly surprised if the AX5-20 doesn't live up to expectations. However, as we all know, hyperbole aside...electronics reach a level of diminishing returns past a certain price point. Improvements, yes, but never night and day like people claim. But at that range, I think you should also check out Gryphon if possible.

Call Mike at Ayre...he knows everything about this stuff

I heard the Octave amp you are referring to with the Dynaudio C20’s and C30’s, and it was very impressive. I too am looking at the Ayre VX5 Twenty to drive a pair of Contour 60’s. I’m just not sure about the amount of power, although the Dyns are 4 ohms and the VX 5 doubles to 350 per channel at 4

Unless your speakers hang out in sub-2ohm territory power isn't a concern with that Ayre amp.