Mono blocks for Revel Salon 1’s recommendation?

Looking at the specs on those, it is important to note if you are using balanced connections that the input impedance is quite low for XLR. As long as the output impedance of your preamp is below 300 ohms, you will be okay. If you go unbalanced there is a lot more room to move with 37kohm input impedance. 

Nice Stereo System.  Hard to justify the word "upgrade" from those Krells.   If they are working to spec., it will be difficult to improve the sound.  Those amps were the grail for many people when they came out.  If you are bored with the sound, then, you could try tube mono amps and start a whole new phase of tinkering.   I am not sure I believe all the rave reviews of the new Class D mono amps.  If you have other reasons for making the change, ie. size, weight, heat, cost of electricity, age, etc..., then, you have many options....

Note: The way things are going, Class A looks to be going extinct in the future... If it was me, I think I would have those Krells checked out for a possible recap and bias and call it a day.  

I agree with @hjdca, the Krell KMA 160 mono amps are first class, you would have to spend $50,000 or more to best the Krells see here.

Mike

I drive mine with amp rolling of michi m8,mcintosh 1.25,bryston 28b3.have not put krell 700mcx or 650 mcx on yet.i did get a satori beryllium tweeter put in both on the front.direct fit but had to drill small hole in opening of tweeter inset of salon to get neg lead to fit. I can always take them out if I sell them.the reviews are fantastic on these salon 1 and they talk about jbl test sound room steve at high performance stero is recapping krell on east coast and George mayer on west coast.between 2 to 3k. You could try d sonic class d direct from factory offers 30 day trial.purify prosper amp module 1.5k 2k into 4 ohms.just a thought . Enjoy the search.and the music

Save a little money and try Wyred 4 Sound SX-1000R.  Plenty of power from B&O Ice Modules.