I run a BSG qol Signal Completion Stage processor which takes my system "to the next level" in imaging. My Thiel CS6 speakers image very well but the qol gives it added depth and focus. I would recommend trying this before buying new gear. TAS and Stereophile reviewed this piece and both reviewers liked it. The audiophiles who have heard my system have had a very strong favorable reaction. One was nearly incredulous and asked, "How do you get so much depth?" A BSG qol comes up for sale ocassionally but you have to watch for it. They usually go for around $1k (they were $4k when new). I bought an extra one in case this one fails.
Another option is the Carver C9. I have one of these also and it works reasonably well but the BSG is better. They sell for cheap so it's not much of a risk to try it. I'm going to sell mine but I haven't gotten around to it.
I haven't heard a BACCH but it seems like it does something similar to the Carver C9. I'm looking forward to hearing this when I have an opportunity.
I've been to three audio shows and I have heard maybe 3 or 4 systems that could match my system in imaging. The MBL 101E's ($80k) were one example. Another was a system with Von Schweikert Ultra 11's ($325k) and a third was with YG Sonja 3.3 ($140k). My point here is that I'm skeptical that you are going to get world class imaging with the budget you propose but if you go with conventional cone speakers you may like the imaging effect better than your ML's. I haven't heard the Ethos but other ML speakers I've heard are no slouches in the imaging department but they have a different character than typical box speakers that's a matter of personal taste. I don't know how well a signal processor will work on an electrostatic speaker but it wouldn't cost too much to find out.