Definitely do the in home comparo. That way you can account for your particular room acoustics and how they interact with your speaker choice. The greatest speaker in the world can be completely hopeless if your room acoustics work against it.
I think you'll find B&W's to have a wholly different sound from Polk so give the B&W's (or any speaker for that matter) a good long listen to give your brain time to recalibrate. Many find the B&W's to be somewhat reserved at first blush, but that's because their bass is very accurate, very fast, and without the pronounced mid-bass hump so many designers like to put into their speakers these days. After a while and a few discs, you'll realize what is right and what is exagerrated, trust me.
Considering the amount of dead presidents you're budgeting, might I suggest something a little further up the food chain? The B&W CDM 7NT's are an order of magnitude better than the 604's, a very good speaker in its own right. They were supplanted by the 700's last year, although that doesn't necessarily mean bettered.
Here is a pair for sale on audiogon or you can see if your dealer can find a set. The CDM NT line utilized the famed Nautilus tweeter and set it on top for time alignment and dispersion characteristics (as with the Naut line). They also employ kevlar mids and kevlar/paper woofers. You can do a web search if you are interested or here is a
review . I have the 7NT's (bias alert!) and find them to be one of the most musical and accurate speakers I've ever heard. Could be why I bought 'em, d'ya think

? There is one downside and it's a biggie: You can forget about your 3805 driving them properly. I tried with my 3803 and it just doesn't have the cajones. Don't get me wrong, it's not bad, there's just so much untapped potential! It's like someone giving you a Ferrari 360 with the caveat you can only drive it using the first two gears. What's the fun in that? Be ready to invest in an amp in the future, it's that simple. One other thing, the CDM NT's transparency comes with a price: They will let you know if you have a weak link in no uncertain terms. Just make sure your front end is up to the task because they are not forgiving...at all. I'm not saying you need Gamut, Krell, or some other exotica, but a $200 Samsung dvd player probably could be improved upon.
Good luck and buy what moves you.