Whats the FATTEST sounding Tube amp to warm up Lean speakers?

The most popular speaker for many years with our M-60 amplifier was the VSM. Very nice match and we showed with Merlin at several CE Shows.

But I would not call the amplifier fat sounding (which usually describes an excess of 2nd harmonic distortion which our amps tend to lack). It just sounds natural. 

The Atma-Sphere OTLs and the Music Reference RM series of amplifiers are not going to "fatten" the sound, they are very flat and just get out of the way. As I mentioned on your other thread old Cary amps and as also recommended here old Conrad Johnson amps will be more suitable, but I also think you're not making the most of your VAC Avatar. Sure it's not  syrupy like some classic tube amps, but it is real. I can't see an amp speaker mismatch because Merlin speakers play well with lots of amps, but I'm not your ears either.

Getting tomorrow an eq i ordered, see what that does in small touches, a db here and there can maybe fix it.

Curious which Conrad Johnson amps in particular have that "Syrupy" sound

Maybe just introduce an equalizer in the chain?