This's my second system now, but the main for long time until I recently assembled the new one with great used components like Thiel and so on.
You can see DIY modification on Adamantes loudspeker, I improved the acoustic performance of the cabinets applying internally some lead sheets glued with polymer MS to ensure a perfect coupling in order to lower the resonance frequency: the result is amazing! Noticeable improvement for bass extension and control.
Also the DAC is DIY based on modified ECHO AUDIOFIRE 4 board and connected to the MacBook via Firewire.
I continue to enjoy a lot the performance of this old setup, very clear and amazing sound specially thinking to the loudspeakers size, for sure a good match with the Sugden A class amplifier, few but very good watts indeed.
Your new copper control knobs does add a touch of elegance. I'm sure you clear coated them so they don't tarnish. I'd like to own the new version of the a21 myself to replace, or switch in and out, with my current system. I'm sure I'd get more use out of it than with tubes. As it is I only use my tube amp for music and occasional movies, and w/ a SS amp I'd use it more for tv too.