Need highly transparent detailed amp---how does Pass XA25 compare to Gamut D100/D200 MKIII

I have a pass labs xa25. I cannot compare it to the amp you are considering. I have not heard it.  Though the xa25 does not get too hot at all. 
It shines in midrange, it’s warm, very quiet, and forgiving with poorly mastered cds. I can only advise regarding the xa25 that you do not utilize  oversized spades on the amp side. They only partially fit. Also a speaker cable of silver and copper 50/50 reveals more detail. All copper and it might sound a bit flat. I’m running them with special 40s in a very small living room. Works well for me. 
Best luck!

Simaudio 760

Pass XA25: exceptional amp, but like reggae, they are Hot Hot Hot. Good choice for Canadians and Alaskans.

I just picked up a used DEMO set of Simaudio MOON 740P (Pre Amp)860A (Amp)- for about $15k. I was afraid of heat from the PASS, and couldn't afford the Luxman 900. The Simaudio makes my KEF REFERENCE 5's sing. Great clear soundstage.

I have been running the pair non-stop for 48 hours (burning in new cables). The pre-amp is COOL and the amp is warm, but certainly not HOT. They are built like tanks and come with a 10yr warranty.

I was told (by a dealer) that the Simaudio gear is better with KEF than GamuT, but there is a listing for a GamuT amp/pre-amp on Audiogon now, from Audio Vision in SF. Steal of a deal if GamuT works for you.

I also have a complete Simaudio system and it is really really nice. I recommend them as well. 740 preamp, 860 amp, 780 streamer/DAC