what solid state amps for the soundlab u-1

The Innersound ESL-300 works fine with U2's so, I would assume it would work equally well with the U-1's. This is one generation removed and I have not heard the current genertion Innersound amps but, one can only assume they would work equally well, or better. The Parasound JC-1's also are reported to work well with Soundlabs.

Yet when it comes to Soundlabs, in my opinion the Atmasphere amps (especially the MA-1 and 2) reign supreme. You must try one of these when you set up a dedicated listening room.

The U2 is now discontinued but, was basically a smaller version of the U1 - a no holds barred electrostatic speaker. In fact I believe Soundlab will still make a U2 if requested. It was not discontinued for being old or out of date, just that Soundlab apparently considered that only one flagship speaker was appropriate. And, probably that their existing offerings (including the newer Millenium series) offered much of the performance of the U2 at a lower cost. I am speculating somewhat on both these points though. Frame features and construction is virtually identical to the U1. The actual panel size in the U2 is somewhere in between the M3 and M2 panels. But the overall speaker size is more akin to the M2.

If you have any interest in the U2 then contact Soundlab and, with a little bit of patience (or a whole lot) you should get a more accurate answer to your questions - tho be it known - it could take a while.