Tubes?

Dave, 

A simple try might be to relieve your McIntosh 601s from doing deep bass duty to the Revels, letting your new subs do the heavy lifting from say 80hZ down from your preamplifier.  I use a Focusrite Clarett 4Pre USB Audio Interface DAC to divide the signal at 80hZ, allowing my 35W per side Music Reference to easily drive my hungry pair of Salk monitors to stadium rock and full orchestral levels.  Pin

If anybody has the balls to do it, an 833-A SET with its grid driven by a tube headphone amp with a transformer output about 600 Ohms and the 1000 Volt B+ to the 833A's through Hammond 1642SE transformer will give you more than enough power. It is not too difficult to build and I will email schematics of how I perfected this. The Hammond transformers are good for 300 ma before the cores saturate and the 833A run at zero grid bias draws about 115 ma. I use this and it is more than enough for my speakers rated at about 85 db.
But if you want more, a GM-100 triode run at 4000 to 5000 volts can give you more if you don't mind the finned anode cap offering instant death to anyone who touches it. It was designed in Bulgaria (the same country which sells glow-in-the-dark cloth from which you can sew together a suit to wear when walking from outside sunlight into a dark movie theater to watch a movie about radiation disasters) by some knuckleheads who wanted to call the 833A a wimpy choice of vacuum tube.

Big VTLs can do justice to your speakers.  I've heard them with Wilsons and some other speakers requiring mucho wattage and tough impedances.  Only Class A/B tube amps are possible.  Otherwise, I would stick with SS.  I wouldn't want a low impedance speaker with low efficiency.  Even my Acoustats and M.L.s ran great on medium power Class A/B amps without the big dynamics or low bass.  I would advise a more efficient speaker or easier to drive impedance.  Harbeth's are an example of a low efficiency, high impedance speaker almost anything can drive well.  Or, choose a speaker with a built-in amp or assist amp for the bass.  They usually can be driven by moderate powered tube amps.

You will probably like tube amps; those with 6550C’s on the outputs are quite nice. Tube amps distort more softly if driven into clipping. Try amps with tubes first, the preamp having tubes is less of a concern as it will rarely be clipped. Certain of the Russian tubes were very good.

drbarney
"But if you want more, a GM-100 triode run at 4000 to 5000 volts can give you more if you don't mind the finned anode cap offering instant death to anyone who touches it." 
I remember back in the day, people running big Krell's on power hungry speakers. Then modifying their AC to cool their music room down. Probably with the suits/litigation now, systems like these would require caution signs and a burn kit to stay legal. 
I do appreciate all of the input. I picked up a McIntosh c2700 yesterday. I'll see how it works out and report back. Dave