Best Tube Amp For Sonus Faber? Or Pass XA-100.5? $6-7,500 Budget, Purchasing Used.

  I don't know the rest of your system but synergy is very important. Also keep in mind that the preamp has a bigger impact on the sound then the amp.

@lostbears , keep also in mind that it's not important the level or class of preamp. more importance plays input/output characteristics of amp/preamp in terms of sensitivity and impedance.

Personally, I haven't heard any Sonus Faber speakers sounding better with tube amp vs. solid state. Mentioned ARC reference mono amps probably would do the best job. VTL or Manley labs also make a line of tube powerhouses, but thinking of heat they generate and upcomming July already making me sweat or setting my AC on maximum during playback...
The combo that impressed me with SF Olympia is Classe CP-880/CAM350 monos. I don't think you can beat that with tubes if same funds spent.

Similar situation with Avalon Ascent MK2 speakers that have somewhat similar characteristics and class. It was sounding clean and precise with BAT VK150 monos, but Pass XA250 simply added BODY to the sound and even perhaps spirit which tube amp couldn't. 

So if there's a choice bettween 

ARC Ref 150
VTL MB250
Pass XA250 

I'd pick pass without doubt 

 I have a pair of Sonus Faber Elipsa SE that I drive with a Audio Research Ref 110. This is a really nice combination. Though at this point I would probably recommend either the Ref 150 or Ref 150se.  ARC is a great match with Sonus Faber and our owned by the same parent company.

 I don't know the rest of your system but synergy is very important. Also keep in mind that the preamp has a bigger impact on the sound then the amp. 

Also, how much heat do the 100.5's generate? I listened to some larger Pass mono's recently, and they turned a huge listening room into a sauna within an hour!

I was hoping I might hear from you, as you and I have shared some attachments to amplifiers, going way back to the Jeff Rowland Model 6's. You've also had quite a few other very good amplifiers, as I recall. 

Your comments on the 100.5's carry a lot of weight, for that reason. It sounds as though you are truly satisfied with them, the midrange, the treble, etc. vs your old tube amps?

I also need to avoid any fully balanced power amplifiers, as my system is single ended.

JC

There is a VAC Phi 300.1 for sale on Audiogon right now for $8,150. You could probably get him down to $7,500 or better. 
That's 150 wpc of tube bliss.

I have to admit though, as someone who has moved on from a 85 wpc tube amp to a pair of Pass Labs XA-100.5 mono-blocks, I am quit happy with the change,