Tube Pre and SS Power? Or the reverse?

I’ve owned an MC462 and a C52 with a variety of tube preamps and power amps rotated into the mix. I think the correct answer is, it depends. But I believe the most logical place to start is tube preamp and SS power amp. Part of the reason is that solid state power is less expensive and more reliable than tubes. I like having a solid state fallback option. I have a fantastic Allnic L-10000 tube preamps and pair it with both tube and SS amplification depending on my mood. 

Off topic: Sounds like you’d like to stick with primarily McIntosh gear. I was of that mindset a few years ago, but I moved away from Mac gear and have been very happy with the results. 

Having owned a audio store 70-30 tube pre,SS amp far better bass and imaging .

+1 for the Tube Preamp / SS PowerAmp combo
I run C12000 with NOS tubes in the preamp, with 2 x MC611s to support the dynamic range, solid consistent power delivery you need across the spectrum.

I agree with @hilde45.

I have Revel f208 speakers which have the same sensitivity as yours. The impedance vs frequency is probably similar. 

I was looking to replace my old, venerable, recapped Mark Levinson #27 power amp with a tube amp. The #27 max power  specs: 100W into  8 ohms, 200W into 4 ohms and 350 W into 2 ohms. This indicates that the #27 has enough current available for complex loads such as the Revels (3.7 ohms at 90 Hz).

I tried several 60-120 W tube power amps but none really had the punch and solid low end, so I stayed with the #27.

I'm using a heavily modified Audio Research LS22 preamp. It replaced my ML #38s preamp. The ML 38s had no punch. Very bland. Big improvement with the LS22.

If the two subs are self-powered, then you've helped the power amp. If not, then tube amps might strain to create the power needed. 

My recommendation is to go with SS power and Tube pre. You'll need to size the power you'll need for your room. My room is moderate size (19' x 14'). The #27 is fine for this room size. You should definitely check out how the amp behaves for different loads.

This combination still has that tube warmth I crave (12AX7 in the phono pre (AR SP-6B phono) and 6DJ8 in the LS22).

Either all tube or all ss, I see no reason to mix. Unless you don't want to deal with many power tubes required for some serious power. But that Chinese stuff they now put in is available and relatively inexpensive, so it should come down to your speakers. If you do mix you will get a transistor sound, anyway. Makes no sense to me.