First tube preamp recommendations (under $5k)


Right now have di20he -> terminator -> he9 -> pass x350.8 -> ATC scm7 / NS5000.
I am thinking of introducing some tubes into my chain. I like the sound I am getting but want to explore what tubes can do to the sound (slight warmth, biggest soundstage, better layering etc etc). Don’t want to go to nuts on price. If price is over $5k would consider if its really exceptional (but for sure not over $10k). Totally fine with used. Balanced would be nice but not mandatory.
So far I am thinking RP7, EVO400, bhk. Any thoughts?
smodtactical
5k trouble free happy listening hours on my REF5se but as others have said, at this level, they are all pretty fine…

Jump in, enjoy the journey and the music….
McIntosh C22 if you’re into the retro looks. C2700 if you want the last tube preamp you’d ever need. 
Read 1 guy preferring motherlode 2 to his Pass XP22. Thats pretty impressive.
I think @teajay also liked ML2 over his microzotl.

But so far have not seen anyone compare ML2 to VAC or ARC. I wonder.
In my opinion the preamp is a good place to start as far as introducing tubes. I would consider a Backert Labs Rumba which can be purchased new under your stated goal of $5k.