You've presented some interesting options. My personal experience is stick with units with 6sn7 tubes. Much more natural sounding. A few of the ones you've mentioned use them. Also as someone mentioned, not all the units you mentioned are fully balanced. The LTA uses an output transformer, not fully balanced circuitry. I believe it's the same with the Backert you mentioned.
If you want fully balanced the Atma-Sphere MP3 that waswntioned is a monster but it's all very upgradeable and doesn't come with a remote stock, you have to add it. Also, it's only XLR I. And our unless you ask for RCA and that's an upcharge. I have Atma-Sphere MA-1 amps and they're the best thing I've ever heard.
I had a Don Sachs model 2 for a while and I absolutely loved the sound. For me, there were 2 downsides, only 1 of which really mattered to me. There wasn't good balance control. For me, as a vinyl guy, records, particularly used ones, sometimes track a little off and being able to move center is something I really like. Also, the khozmo volume control clicks when you use the remote. I didn't care about that though. Honestly, I'd the balance was better, I'd probably still have it.
Someone mentioned ARC. Ralph at Atma-Sphere does not consider them fully balanced. I can't fully explain that. You'd have to talk to him but he's very available and will happily take a phone call.
Someone else mentioned a ModWright. I have an LS100 and love it. It's not fully balanced. I don't particularly care. It sounds amazing. I'm likely going to send it to Dan at ModWright and have him add a lundahl output transformer to have a balanced out as it will maybe work even better with my Atma-Sphere amps. They make 1 fully balanced amp but it's over 10k. I think the lres a new ML kndel that they put out that uses transformers as well.