Seeking Suggestions on Preamp Upgrade (CJ, Aesthetix, EAR)

Hi  david, 
you have asked an open question. Soon enough, there will be just about many different preamp recommended to you. 
what is your music genre and your sound preference like? i.e laid back, relax? euphoric? vivid? big voice , wide soundstage?

there are many different preamp that will be good only in certain aspects of audio reproduction. It's very difficult to achieve absolute detail with richness and tonally accurate plus wide open soundstage if you listen to majestic performance like in a classical recording. only a handful with a heavenly price tag  preamps can do well in everything.
-phil

What you need is to purchase a reasonable good preamp that response well to tube rolling. Most people use tubes to fine tune the degree of warmth.

EAR , Mapletree audio and Joule Electra are some of the tube pre that i find may have more warmth compared to CJ , ARC, Allnic and alikes.. do be aware that within its product line, there are also some difference in their sound characteristic too. PrimaLuna is another suggestion, however, personally i feel it's does not sound laid back, much better for music with singers. 

you have to judge for yourself how distant sound you feel that's right for you. There are many preamp that provide warmth but it's much more difficult to strike the right balance mix of detail, articulation and warmth that suited to your taste, hence tube and cable rolling sometimes can be quite handy. 
-phil