Yeah, there is theoretical problems with everything that only money seems to solve (at least in advertising)! I have also been considering and reading about no-feedback designs(and may start another thread). I am not sure how to conduct a meaningful subjective comparison to more regular SS amps, though, unless I compared a lot of them.
A compromise of those amps to keep in mind is a high output impedance. People like Atma-sphere amps with Magnepan, so it shouldn't be a big deal for you, but the on-paper issue is a voltage drop to the speaker proportionally related by the calculated damping factor. Your speaker, of course is 4.5ohms, which is low but not really low. I am really just suggesting to be aware of that measurement before purchase.
Ayre is another company that advertises no-feedback amps, and Spectron has their ultra-fast control loop which may be interesting to you.
A compromise of those amps to keep in mind is a high output impedance. People like Atma-sphere amps with Magnepan, so it shouldn't be a big deal for you, but the on-paper issue is a voltage drop to the speaker proportionally related by the calculated damping factor. Your speaker, of course is 4.5ohms, which is low but not really low. I am really just suggesting to be aware of that measurement before purchase.
Ayre is another company that advertises no-feedback amps, and Spectron has their ultra-fast control loop which may be interesting to you.