I have the LS 50's which are very solid performers in my opinion. In many ways (treble extension/smoothness and overall soundstage width especially) they best the monstrous Klipsch CF-1's that I run in my main rig with a certain amount of ease. I know the LS 70's are supposed to be significantly better (bi-ampable as well) and the LS 90's a larger step still above that. IMO, if that really is the case - a price of $200 or less would be a very very good on them if they function properly.
I would be willing to bet that a bi-amped setup with a decent pair of amps would sound heavenly with them.