Considering a new amp for my Vandersteen Quatro CT

I also have a pair of the Vandersteen Quatro CT and use the Ayre 5 Twenty-series products (KX-5, QX-5 and VX-5 Twenty’s) and the sound is great. That said, I am looking to upgrade my speakers to possibly the Kento Carbon or Model 7 mkii if or when I find a suitable used pair at a good/great price.

Have you considered the Vandersteen M5-HPA amp? For what it’s worth; While I have not heard them, I was told they sound better than the Ayre amps.  There is a used pair for sale in Colorado.  They're asking $11.9K

I will echo Jim’s @tomic601 recommendation of the Vandersteen mono’s. No doubt an obvious system symmetry approach.

But, if more than you want to ‘pony up’, I recently added a pair of used but excellant Belles MB-200 mono blocks in my system driving my Treo’s. Belles just knows how to make everything he makes musical. Also, a great fit with my ‘new’ Belles Aria Signature preamp. Happy camper.

@twoleftears Very good recommendation I always forget about Belles.  

Belles Virtuoso power amp

I have 5As powered by Ayre and it's a very good match.  That said, Richard V typically demos his speakers with ARC electronics, so that might be something to keep in mind.  And, although I have only heard them briefly, the Vandersteen amps are impressive, and they were designed to match with your speakers.  My local dealer, who sells all three brands, says he likes the Vandy amps better on Vandy speakers than either ARC or D'Agostino. 

Whatever you choose to do, happy listening!

McCormack and Vandy have a long history of playing well together. I’ll give you two options of excellent candidates, but I’d recommend the cheaper version because your speakers have powered subs and it’s got a lot of Steve’s latest upgrades already installed so you’re getting a SOTA amp at a screaming bargain.  My only recommendation with either amp would be to send it to SMcAudio and have the gravity base installed — by all accounts it takes the amp up several notches in performance.  I’m having my DNA-0.5 RevA upgraded now and sprung for the gravity base.  To me this will be a keeper amp for life  

https://www.usaudiomart.com/details/649881609-mccormack-dna-500/

https://www.usaudiomart.com/details/649847769-smc-modded-mccormack-dna125-power-amp-excellent-condition/