Quad ESLs - I have some questions


Recently I heard the latest model Quad ESL, 2905 I think, and it was a love at first listen kinda thing.  Of course I began looking at used Quad ESLs, and I am curious what the significant differences are between the 63s and the later models like 2805s and 2905s?  Used 63s are in my price range now, 2805s etc would require some patience, so I'm curious if the SQ, reliability, power handling, or other differences are worth the additional cost?  W/r/t 63s, should I be wary if they've been rebuilt. or should that be comforting if the rebuilder has a good reputation?  Anything else I should know?

The 2905s I heard were powered by a Bob Carver Crimson 275, the dealer said my BAT VK-55 would also be a great match.  I listen to singer/songwriter/acoustic/Americana/indy/alternative music with some experimental, jazz, chamber, and classical piano thrown in.  Think First Aid Kit, Jeff Parker, Wilco, Michael Kiwanuka, Gordon Lightfoot, Everything but the Girl, Anna Meredith, generally 85-93 dBs.  Room is 12x20x8, set up for one listener, fairly well treated.  Current speakers are Thiel CS-2.3s.  Also considering Zus and Devores.
128x128thosb
No brainer with the Sound Lab. Most everyone knows they kill Martin Logans etc. I was once convinced that dynamic drivers were the king of bass. Not so. Full range huge Sound lab electrostatic panels produce the cleanest, lowest distortion, detailed bass at high volume levels. Dipole bass. I am listening to my Martin logans right now. They stink. My old Acoustat 2 plus 2's sounded better. I might have to rob a bank for the Sound Lab's. They aren't cheap. Who cares about the size of them. Go big or go home. 
Sound Labs are the MOST coveted loudspeaker for any electrostatic fan. You have reached heaven when you can own a pair. Lower mass diaphragm plus its the engineering of the transformer that makes a huge difference. Martin logan uses 2 transformers both in the signal path in their loudspeakers. One to couple and the other to increase efficiency.  I am listening to my Logans now and they sound like sound coming from a metal trash can. Martin logan are just a STARTING point for an electrostatic speaker lover. 
Good advice, thanks all.  As usual, my list of options had broadened (Harbeth, Daedalus, Soundlab, Emminent, Bache) rather than narrowed. 
I guess I will stay away from the Quad ESLs for now.  I don't need a right of passage or another project right now or a fickle love interest, surely there are other paths to audio nirvana.  Thanks everyone for their comments and sharing your experiences!
thosb, keep an eye out on the used market. Both Acoustat and Sound Labs speakers are indestructible as long as nobody has gone into them.
You might trip across a pair at a good price. Once you have lived with one of these there is no going back. Everything else makes Kate Bush sound like Brad Roberts:)