"Double" bi-amping a good idea?

If you really want to improve your sound sell the Bel Cantos and buy an InnerSound ESL amp. The ESL amp was specifically designed to drive the complex loads that electrostatic hybrids present, and a single stereo ESL amp will give you just as much power (if not more) than the 4 bridged Bel Cantos you are considering. If you did a vertical bi-amp with two ESL amps you'd have more power/volume than your ears could possibly stand and better sound to boot.

Tekunda, another thing to try before you buy anything else would be to use the Bel Canto amps in their stereo mode to drive the ESL panel and bass section of each speaker separately. This is the configuration for vertical bi-amping -- right now, with the amps in mono you are horizontal bi-amping. My guess is that vertical biamping would result in better quality sound -- not louder -- but better. Try that and let us know what you think. If that still doesn't float your boat then you may want to consider my previous suggestion of going to the InnerSound amps. I doubt that using two pairs of the Bel Canto amps will give you what you are looking for.

I can't comment on your speaker-amp combination, but years ago I tried it with 2 pair of the original BEL 1001s and a pair of B & W 808s, and even thogh the speakers were quite efficient, there was a noticeable gain in clarity in the midrange and control and definition in the bass,