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

If the 60.5’s seem likely to power your speakers, I would re-read the Stereophile review of them, where John Atkinson called them the finest amps he has ever auditioned.

There are very, very few reviewers whose opinions I respect, and JA is definitely NOT one of them.
Frankly, I don’t think JA can hear at all. I learned to ignore any comment from him decades ago.

That’s not a swipe at the XA-60.5’s, I’m sure they work fine with the right speakers.

The ARC Ref 5 preamp is not a great combo with any Pass labs poweramp. We auditioned it with different Pass poweramps.

The limitation is based on the fact that stage depth and width is not like other pre amps are able to create.  It makes the stage less deep and wide. But also in speed and timing it is not at a reference level. Beside this the level in details is also limited. We could proof both in details in the high frequencies and even in the layering in the middle frequencies that they ARC Ref 5 was not able to show the these information we could create.

Both XP-20 ( which I owned for 2 years) and the ARC Ref 5 preamp are also limited in individual focus of instruments and voices. 

This means that they are both not able to create an intimate and physical image of voices and instruments.

I had different conversations with Desmond Harrington about the lack of individual focus of voices and instruments.

You need to understand how voices and instruments are being projected into space and how big they are.

I created Statement Audio Pro measurement what brings any Pass Labs poweramp to a superior and new level.

It creates a superior level in details but also in diversity in sound. There are so much more layers compared to the XP-20 and ARC Ref5.

I can create an even higher level about 6 times each year. We are at a level now that the energy of instruments can be felt separately. And even the energy of instruments can stand in a different perspective of depth.

The acoustics limits the quality of a poweramp so much. Without roomcorrection it is not possible to create this stunning level we can achieve at this moment.

We also can play a lot louder in pure class A with Pass labs X-series amps compared to the XP-20.

Now we have ideas to use conservatorium students to explain people what diversity in sound means and does with our emotion. We want to use instruments and real voices to show people how small and direct they are in real.

We can proof now that with Statement Audio Pro music comes so much closer to how music sounds in real. We are born perfectionists and we want to create the best level in realism possible.

I can create an even higher level about 6 times each year. We are at a level now that the energy of instruments can be felt separately. And even the energy of instruments can stand in a different perspective of depth.

@nightfall , sorry JC, once bo stumbles onto your thread, it is destroyed with mind-numbing audio mumble jumble.
It is akin to termites stumbling onto your home.

Did you get your VAC amp yet?
Which model did you buy?
What do you think?

Since nobody knows what 3D sound is, nobody knows what "real" sounds like, nobody appreciates diversity, everybody ends up hating his or her system, everything except what Bo likes is 2D and non-diverse, and we’re all ignorant, just do yourself a favor and buy Pass, Monitor, and Secret Sauce from Bo--all of your audio woes will be healed for life and you can die happy. Something like that, unless my decoder ring is broken.

nightfall, 
Pass XA-100.5 would be a great option. Also consider some McIntosh SS amps or integrateds such as the MA7900, MA8900, MA6700 integrateds or the MC350 stereo power amp. McIntosh and Sonus Faber have good sonic synergy together.
I've heard your speakers driven by one of these McIntosh amps before at the store and IMO they sounded great together. 
AR amps would be another good option for your speakers. 

I also heard your your speakers driven by the Musical Fidelity Nu-Vista 600 integrated amp before and I thought they were paired very well together. 
Speaker cables also need to taken into consideration in getting a perfect match with your equipments. 

Some Lamm and higher end Primaluna would be a good option for your speakers.