I don't know, man.
If it were me, and money wasn't the issue, and based off your initial post about $100,000 or $180,000 it certainly doesn't sound like it, then I'd bring in the top 3-5 amps all at the same time and just find out the actual answer. Take the guess work and forums posts out of it.
Pretty much nobody has the money for that, so we all speculate and say "what's better" based on guesses. The number of people who've actually heard the MSB Electrostatic amp are only a handful, and I don't mean tried it in passing at a Show or a meet. Then let alone had one at home for some real quality time, and finally who've compared one at home to something else at the top is likely so few that you wouldn't hear from them even here. If I were playing up in that league, I'd just throw out a feeler thread like this, try to get some consensus on the top 5, then buy all of them. The ones that you don't like, you'll be able to move them for little loss even if you buy new.
This is just my take on the situation, but I don't know why you'd do it any other way if you've got the cash and the time investment isn't even that much.
Top 5 I know of:
1. MSB Electrostatic amp (~$40,000)
2. DIY T2 (might be able to buy someone's for ~$15,000, otherwise it's around $10,000 + find a builder + wait a long time, thus I'd throw some money at it)
3. RSA Thunderbolt II (~$7,000 last I heard)
4. BHSE (~$6,000)
5. Not sure what else is up in this league.
The benefit of going electrostatic is that there aren't that many amps. Most people say the DIY T2 (now i think it's like rev.2) is the end of the line, then Audio Addict said the updated Thunderbolt II was it. Then there's the MSB Electrostatic at the top of the money pile. That's only like 3 amps. The BHSE, just based on my reading, is never in that league, it's kind of the "everyman's" best answer, while the other ones either cost a ton more or are hard to track down if you just want to pay a reasonable price.
Anyway, I'm no authority on this, but when you start out talking megabucks, then I'd just solve the problem, not cut any corners, and enjoy my system until the end of my days. Good luck.