My experience with surround sound (usually found in audio systems for home theatre) is that it relies greatly on the centre speaker to create the sound stage. This is obvious for movie sound tracks, but also prevalent on surround sound music mixes, such as those found on SACDs and DVD-As.One of the real benefits of digital surround sound is that it can combine both the highest digital quality available along with amazing 5.1 surround sound mixes. A win/win for anyone who has longed for more than just two channels to present the music with.
But traditional ESLs (electrostatic loudspeakers), such as the venerable Martin Logan Sequels and the Sequel IIs, were a product of 2 channel stereo sound reproduction. They were never intended to be part of surround sound speaker set. Not that they wouldn’t be great at it, just that the nuances of the sound stage they have been designed to create would certainly be lost once you throw the centre speaker into the mix, which pretty much destroys any intended 2 channel sound stage anyway.
This isn’t all cons, however. In very difficult rooms or where the rooms esthetics trump the ideal speaker placement, a centre channel can serve to save the day. But with good room acoustics and a reasonable option of placements for ESLs, a pure two channel signal path will reproduce a more engaging and intimate soundstage every time.