Nice one Rob D, it's always great news to hear that ML fully supported their warranty and replaced your BF210 with a new one. Now that's service! And yes, this type of customer support is rarer than the Tasmanian Tiger! At one point I was actually thinking whether ML/ the dealer would eventually replace the entire unit ... and so they did! Outstanding.
Regarding whether ML subs are the best or nothing comes close, I guess just depends on your particular system. Just like cables and accessories, it's system dependent. For example, when I was on the hunt for that perfect matching to the CLX's, I did try about 6 different ones. From REL, Paradigm, Vandy, Velodyne, to one of our local Aussie brands, SGR I think it was. The other one I can't quite recall. Nearly all of these were fairly less in price compared to the BF series, so that was my rationale to see if any of the others would match well. Anyway, at the end of the day, the BF series seemed to be part of the missing puzzle, and then it all came together when I finally installed one, after nearly 3yrs of trial and error.
The "BF" concept clearly makes more sense, coming from the very same company that produces the electrostats. There's just something that's very right about the whole presentation. It's very well balanced, matches extremely well with ARC once dialed in correctly and overall performance is quite natural, not too much of anything nor is bass heavy.
Natural music is not bass heavy and doesn't even go anywhere lower than 20Hz in the first place. The human ear can only hear within the range of 20Hz to 20KHz, and that's perfect human hearing. The majority of us don't have perfect hearing, although we would like to proclaim that we can hear anything & everything. As we age, our "perfect " hearing ability diminishes. So I'm not even interested in subs going below 20Hz...and most natural recordings don't have music that's below that range, let alone even close to 20Hz. Even those excess HF's of 40KHz and above, forget it! We simply can't hear such HF's. Whoever claims they can must be a werewolf!
HT OTOH is thrilling and exciting, and most of it is artificial enhancements in sound, nothing much in terms of naturalness at all. For those who love earth shattering bass, obviously need to find the right sub/s to match well with that kind of gear. It's always great to have choices and be able to compare, just find the right one that suits your system gear and finances. It's like finding the right wifey...
Cheers matey, and enjoy those fine tunes!
Btw, Hope all is ok with your health...