You have done a great job so far. There are other more important fish to fry besides a Walker Prothenium which IMHO is over the hill in terms of complexity and I am not in any way in favor of that tonearm.
You and I have very similar tastes in HifI gear. Both our systems are based on ESLs and subwoofers. We both use Digital preamplifiers. My first suggestion is to get rid of the Velodyne subwoofers and get a pair of ML Balanced Force 212s.
Next will be to trade the Trinnov in for a DEQX Pre 4 or 8. I almost bought the Amethyst until I got wind of the new DEQX units. They have far more flexibility than the Trinnov particularly in bass management. I will be getting mine in about a month. I was selected along with 119 other people to test the beta version of the software. We get a discount on the units. I think we are all getting Pre 8s which has a full 4 way crossover. I am not sure how ML set up the step up transformers of your speakers. The Sound Labs uses a bass and a treble transformer for each speaker. I am going to biamp the speakers using one amp to drive the treble transformer and the other to drive the bass. The crossover is at 5000 Hz.
After this play around with cartridges and other sources. I use a Channel D Seta L Plus and use the computer to do the RIAA correction. I can raid my friend's record collections and make perfect replications in 24/192. You can use the vinyl recording software with any phono stage. I have started to stream with Qobuz and can buy files through them. It is a great way to keep up with new music. I still buy records. It is a habit I can not seem to shake. I also use a Sota Cosmos Eclipse Vacuum with a Schroder CB on it. The only other turntable I have my eye on is the Dohmann Helix 1. I would put a Schroder LT on it. I doubt this will ever happen as it is very hard to justify. I use three cartridges, the MC Diamond, the Atlas Lambda SL and the MSL Signature Platinum. At this moment I am not interested in other cartridges.
There is a new control unit for your Sota. Contact Donna and get in line.
I am getting a pair of Audiomica Allbit Consequence power cables for the SLs. skos brought a pair over telling me he heard them on another SL system and could not believe the difference. I thought he was joking! These cables have some type of filter. Darn if they did not increase low level detail beyond the realm of the psychological. For me to pony up thousands for power cables is a novel event. Something is getting to the diaphragms that is polluting the speakers and I have my own power transformer on the street. I do not know if the same result would occur with your MLs but I would bet it will. You might message skos about them.
I am going to use the MA 2s (Atma-Sphere) to drive the bass transformers as they are uniquely suited to that role. I will need a solid state amplifier with a very low output impedance to drive the treble transformers. Roger West suggested the Benchmark AHB2s but I was thinking of something more like the PAS XA 100.8s. Ralph would like to sell me his class D amps. This is going to be a tough decision.