Need a power amp for a pair of ATC SCM 11's

i would think the wyred unit will do well w the atc's

atc's sound great but need tremendous power and grip to drive them well

w4s unit will do that, and it has a nice tonality to boot

i would take that over an old quad amp, as they are old, may need recap and other service 

ATC makes amps.  Just sayin'.

ATC is very revealing and inefficient from what I've heard. My current class d sounds absolutely great in 2 out of 3 of my speakers. My current mains which are very revealing and also happen to be the least efficient not as much. AB much better..
Also was running a Lyngdorf TDIA 2170 last year which I hold in high esteem as far as class d amps go. Sounded phenominal with efficient speakers. 4 ohm low efficiency not so much.  Ymmv.
 Had a Wyred dac one time but never one of their amps. 

FWIW, I'm currently using the same Wyred ST 500MKII which I found used. Love it a as great all around amp, flexible and easy to transport. I also have the STP-SE so it prob helps that I've kept things in the family and can run fully differential.

I've used it with a few pairs of speakers (incl bookshelfs) and it always sounded good. I used to right next to SYVANE 50 watt monoblocks and to my ear it was not outclassed. The bass seemed better than the tube gear, maybe a bit more definition with the Wyred but the tube amps seemed to have a slightly larger soundstage. The Wyred was not blown out of the water which was really what I wanted to check out. 

I was running a Forte Model 3 before this and the Wyred seems better all around for my use. Enjoy. 

The Quad 909 is a nice neutral amp slightly on the warm sound . It would be a nice match with the ATC . 
Another option used would be a Mccormack if you can find some on the market as they dont show up very often .
What ever you get remember the ATC need amps so go with a amplifier capable to give a lot of current . Dynamics will suffer if not .