I have spend a good bit of time with the current line as a whole but have never heard the 35. The RB81s replaced the 35s I believe.
I like them a lot for what they are. They are pretty balanced and reach down pretty low in the bass. Their drivers seem to be pretty good and have lots of detail with no odd break up nodes (I can hear...). Klipsches cabinets leave a lot to be desired but you get what you pay for...
I have put a few HT systems together for friends than do not want to break the bank but want good sound. I alway recommend Klipsch and after a demo (with no brand push from me) they have always chosen the Klipsch over other speakers in there price range (Paradigms, Energy, etc). They will have vertually limitless volume with very little wattage and hold there own at both loud and low volumes.
But the problem with them for you will be you are coming from Quads... a much better speaker IMO. The Klipsch will VERY different! But for there price they are worth a try if you just want a different flavor for awhile. I would recommend getting the RB81s though because they are the current model and will be easier to sell when you are done. They go for $300-400 on ebay.
For a music only system, they have some coloration but it is minimal when you consider the price! You could always buy a pair of RB-81s from Crutchfield and send them back if they are not for you. They have a 30 day no questions asked return policy. BUT you would have to pay retail... Your tube amp should tame some of their sharpness and be a good match by the way.
RB-81 vs B&W 805s:
Yea not a fair price war but I have had them in the same room and their performance difference does not match the price difference. The sound stage is smaller on the RB-81. The 805s highs are a little softer and have more air. The mids are a little more flushed out on the 805s. BUT the Klipsches have presence and dynamic punch that make the 805s seem line snoozers... While not as refined the punchy, clean, quick bass in combination of the forward mids and highs of the Klipsch may be what you are looking for in rock music. But it may make soft jazz seem colored but you can just roll out the Quads for that. Don't get me wrong the 805s are better all round but they are 3 time the price too.
All in all I think they are a safe buy for the money.
