B&W 702S2 vs Polk Legend L800 SDA vs Klipsch Cornwall

That is three different corners of hi-fi sound. Polk=dull, B&W=detailed, Klipsch Cornwall=Well, they are what they are. I think you need to pick the kind of sound you would like to hear. If you were thinking about Jubes, maybe some used LaScalas? 

I have owned all three of these brands before. Personally I think the Cornwall IV is the most interesting on that list. B&W is rough in it frequency response and wears out my ears (I owned the 703, older but very similar to the current 702s) you will spend a lot of time chasing the “perfect” electrics to fix their sound. I hated my polks. A total snoozer I don’t even remember the model my time was so short with them. Audioaholics say they are good so they probably are but still a total pass for me