D'Agostino vs. Ayre

Yes I've had both in my system.
Ayre: incisive, fast, obsessive. Stunning with Vandersteens.
D'Agostino: palpable,organic, transparent. Astonishing with Magicos or YGs. 
Choose your poison. 
There is no antidote. 

100% agree with khrys . I will  add that the Ayre can sound a little thin/brittle depending on speakers used.    I would also add AudioNet to your list. Fast and detailed, with nice dense  fleshed out images.

I agree wholeheartedly with your assessment of the Ayre's. They are incicively addicting and very musical, but sometimes a touch lean in the mids and sometimes a tad bit harsh on top. I plan to power a pair of Wilson Alexia's. And right now, I have Ayre MX-R Twenties and AtmaSphere MA-1 3.3s in house. The AtmaSpheres are organically rich in the mids and crystalline on top. Never syrupy, but highly transparent. Piano is amazingly realistic, guitar strings blossom with pure harmonics. Not enough bass for some recordings, though. I could imagine the AtmaSpheres to be perfect with a powered woofer. I will try to audition a D'Agostino S-250.

The Dags are amazing with the Wilson line. Great liquidity and system synergy. Almost tube like but still has tremendous grip. Ayre is a great company and the Ayre MX-20 amps are great with Wilson, but the Dag/Wilson combo (for speakers Sasha and above) has that certain Je ne sais quoi that must be heard to be appreciated. I had the Dag stereo amp in house with Sashas a while back and they were simply the best American made ss I have ever heard with Wilsons. I've heard great things about DartZeel, Gryphon, Tenor and Soulution among others with Wilson, but do not have first hand experience with those combos. 

Knowing now you are powering Alexias the D’ags are the clear choice over the MXR-20s.
If you want them to sing and dance for their supper then high powered tubes are essential.
VTL Siegfrieds or ARC 750 SEs are the best matches for Alexias I’ve heard so far.
Just heard the Boulder 2160 with Alexias recently which was revelatory so I reserve the right to equiviquate and retract previous musings with unassailable certainty.