You have gotten plenty of input, but I thought I would chime in because I have 805's and have hooked them to many different amps. The sensitivity is definitely an issue. I have had them hooked to even some higher power tube amps(not SET) like Cary, McIntosh, etc, and they just didn't sound good. They definitely sound significantly better with more power.
As far as replacing them, if you really like the B&W sound, you won't be happy with vintage Klipsch, IMHO. But getting new speakers is a whole different ball game :) Good Luck!
As far as replacing them, if you really like the B&W sound, you won't be happy with vintage Klipsch, IMHO. But getting new speakers is a whole different ball game :) Good Luck!