First foray into tube amps

I think in most of these cases, given the context you’ve provided - tubes will provide the mid-range magic you seek. You’ll usually give up some bass slam and add in some slight "bloom" in that frequency range, with tubes - how much comes down to the specific amp and speakers. But I rather like the net effect of a good strong tube amp on bass. Treble on tube amps is typically nice airy smooth and sweet - no rolloff, no problems (like with some SS amps being aggressive, etched or splashy).

Where to start? Just start. Period. Avoid a severe mismatch (unlikely based on your options), pick what strikes your fancy, and start learning about how YOU react to tubes :) All those tube amps will sound a bit different, and rolling tubes further multiplies the variations. But they’ll all sound like tubes, and this should be quite distinct from SS.

Are you in a location where there are dealers that will allow you to audition an amp in your system for a few days? (you’ll pay a deposit to cover risk). The usual question is synergy between amp and speaker. 

The McI is an old standby, my understanding is that this model has gone through various iterations, I do not know what version shines-- ask a McI board if not here.

Hard to predict what you’ll like. One factor is what tubes are used? Some tubes are more scarce as NOS, particularly power tubes. Being able to run new production is an advantage, but if you consider NOS, you want to know that those are not unobatinium. 

Some of what you will get is "brand dogma" -not necessarily meaningful to answer your question. 

I've tried quite a few power amps in my system lately, including ones from Cary and CJ.

None of them approach the clarity, slam, and effortless musicality of my ML No. 27 power amp. It matches to my Revel f208 speakers extremely well.

I've decided to stick with SS for the power amp. The hassles associated with tube amps and the lack of any clear advantage made the decision easy.

However, my preamp and phono preamps are fully tubed. They are the ones that determine the quality of the sound in my system. They beat SS phono and line level equipment hands down.

My recommendation is to use tubes in phono and line level but use a beefy (and good sounding, of course) power amp to drive the speakers. Vendors such as Mark Levinson and Bryston come first to mind.

I would wholeheartedly suggest you check out Aric Audio; Aric makes amazing tube gear and he's a great guy who I'm sure would be happy to discuss it all with you, even if you don't end up buying from him.

Galion Audio…..super quality and value off the charts. I don’t know your speaker sensitivity. They also offer a free return window.