Best speaker for BC2 amps.....

Ditto for me. Have owned three different generations of the Merlin VSM (Gen 3, SE, and Millennium) and am very happy with it. I understand Bobby of Merlin used Blue Circle amps to demo his speakers in past Shows before going with Joule Electra OTLs.

Also consider Spendor and Harbeth. I use the Spendor SP 1/2 in my BC based system, and the combo is magic. As for the Martin Logans, Gilbert uses them in his reference system. In fact, I think there's a link to his system on the BC website.

I'd vote with the Spendor and Harbeth crowd. When I heard BC 2.1's with Merlins, they were very assertive. If you like that, fine. Nothing wrong with it. But if you prefer a less pushy sound, try Spendor SP 1/2's or Harbeth Compact 7's. Spendors a tad more sensuous, Harbeths have much better bass. Both among the best. Dark horse, with more personality than the BBC speakers: Reynaud Offrandes. More expensive but probably a very fine fit.