Im looking for the next upgrade. I'm not real sure which way I want to go Help!

I used to have a system very similar to yours.  None of those components are still in my system.  So really you can go in any direction.  

Now my ML's were CLS and needed a behemoth amp to drive them.  i don't know how many watts your ESLs need with their powered woofers.  If you can get away wtiht 20 or 30 watts, I love the electrostatic sound.  

Assuming that is true, the easiest way for you to make a big change in your sound is with an integrated tube amp.  If you must to SS, I highly recomment the Kinki Studios XXXXX+  (I have one but can't remember the initials).  Great integrated.

JErry

I am looking for a fuller sound I’ve heard ESL 13’s with a Gryphon Mephistopheles and was very impressed. Right now in thinking what I have is on the anemic side

I don’t think using the streamer as a preamp is doing you any favors at all, and I’d look to try a good tube preamp that I bet will yield improvements across the board. What’s your budget? I’d highly recommend looking at this Don Sachs pre that will add life and tonal richness to your system yet still with excellent, natural detail, and it’s only $2450. If it doesn’t work just turn around and sell it for little/no loss, but many say this is an end-game preamp. Definitely worth a shot for what you’re looking for IMHO and could save you big $$$ over other options.  My bet is it’ll blow you away just going by what you’re hearing now and how elated other Sachs pre owners have been.  Just my $0.02 FWIW.

https://www.usaudiomart.com/details/649919944-don-sachs-model-2-line-stage-preamp/

The MLs will sing with good tube pre and amp combo.  Adding a sub can be fun if it's set up well, but I'd definitely make letting the MLs breath the higher priority.

I use a pair of ML Impressions with an ARC tubed preamp and a Classe two channel amp. It has delighted me for years, and I have never felt a sense of fatigue and or any kind of thin sound.