The Music Room has D'Agostino, VTL, Parasound, and Nagra amps currently. Others will make visits as checks and balances.
For development in the factory, add Spectral to the list. Again, others rotate in and out.
In dealer events the past 18 months in the US, we have used D'Agostino, ARC, Doshi, VTL, Boulder, McIntosh, Naim, Bryston, Ayre, Constellation, Mytek, Aesthetix, T+A, Moon, and I'm sure some others I am not remembering. Internationally, you could add DarTzeel, Soulution, CH Precision, Krell, etc.
Still there are others that have been more popular in the past including Classe, LAMM, CJ, Mark Levinson, Rowland.
I use a Nagra/Pass combo on Yvettes at home. I've had the Pass since the mid 90's.
As long as the amp drives the speaker properly, just choose the one you prefer.