Warm Tube Amp(s) to Tame Hyper-Accurate Speakers?

I may have said this before but if you are not fond of steak, no amount of seasoning or preparation work is likely to change that fact.

So it is with a speaker.  If your speakers are restricting what music you listen to, something is fundamentally wrong with that choice.  And then to make matters worse, spending thousands of dollars hoping force the situation is usually money poorly spent as well.

Putting components together is akin to a talented chef choosing the right seasonings for a given entree--but don't expect him to turn steak into lobster.

@alphonsodamato -

     What tubes are you using in your 275 (small signal and power) and preamp?

     How much absorptive material in the room?

     Lots of hard surfaces, between you and the speakers?

     Is your music strident, with all sources?

+1 @rodman99999 is asking fundamental questions for the OP. If these are not answered, then this really becomes a thread about mindless gear swapping.

Try any of the earlier Cary Audio preamps/amps. You'll be swimming in syrup...

Before any meaningful "solutions" can be offered, we need to understand the problem.  First, saying the mids and highs are too much could mean the same as the bass and upper bass is too thin--after all, tonal qualities are about relative balance of frequencies.  Is this a case of someone wanting more bass or warm in the upper bass rather than having issues with mids and highs?\

Could there actually be a problem with the gear or set up?  Has he had anyone else listen to diagnose if there is something completely out of place?  Has he tried any other gear?

Is this a matter of particular taste?  It would be helpful if the OP were to offer comparisons with other systems he has heard and liked or disliked. 

I have heard the MC275 VI and did not like it at all, but not really because it sounded bright--mainly because it sounded lifeless and unengaging.  It did have a slightly hard and brittle sound, not unlike other KT88 amps, and perhaps this is the issue.