Dont' know about B&W, but Paradigm does not sell online. If you find a "dealer" selling online, they are not authorized and you won't get warranty coverage.
I have a severly limited number of dealers near me, so I can only give you my limited experience. You can always haggle with the sales rep and try to get a better price. I think something like 10-15% off would be "reasonable". I wouldn't pay MSRP anywhere. Usually you will get some discount if you buy multiple items. In general, you will find you get better deals if you are a repeat customer at dedicated audio stores. It takes building a relationship with the dealer or better yet a specific sales rep. I'm sure there are exceptions, but they are few and far between from what I have seen.