Two of the ESL's major limitations---low bass and maximum SPL capability, now have a common solution (okay, not complete, but significant): the GR Research/Rythmik OB/Dipole Subwoofer.
The ESL has long been known to be impossible to integrate with a sub to a degree acceptable with perfectionists. That is no longer the case: the OB sub is finding favour amongst owners of not just QUADS, but also Maggies, Martin Logans, Acoustats, Eminent Technology LFT's, even horn loudspeakers. Oh yeah, and dynamic/cone/box designs.
Taking the low bass out of the ESL panels (and the power amp driving them) allows them to play louder (okay, still not that loud) and cleaner.
Read all about the sub on the AudioCircle GR Research Forum.