Electrostatic Speakers/SS amp - what tube preamp?

I will second the SF choice.The SFL-2 is much better than the SFL-1{not sure where Sig.version comes in}.Possibly,the terra Song SS-1 or Marsh P2000.Are you using digital or analog.Digital always sounded better using this amp than did my 46K analog set-up.You will want something with a little sparkle up-top.

I will third the SF recommendation.

Gilbert Yeung at Blue Circle loves Martin Logans, and uses a pair of Odessey and a pair of CLS (amount some other brands) to tweek and test his designs.

His pair of CLS are pink (a custom job just for him by Martin Logan as a joke).

So put his tube preamps on your list. The matching amp to his BC21 and BC21.1 preamps is a solid state amp (BC22). Many also use his BC3 preamp with either a BC22 or a BC26.

Just curious. Do the Blue Circles have a balanced option?

Unsound, I'm realy curious about 50Ohms...
If that is the case or near arround even SF can be an issue of compatibility. I might be wrong if SF is transformer-coupled like AN...?