I am not going to directly address your question, thinking it better to comment about other issues raised by your thread.
If possible (and if I were you, I would try very hard to expand the meaning of "possible"), you should get your speakers farther off the wall than 12" to 18". Assuming that they will be closer to the wall than ideal, you should avoid any speaker that is rear ported.
You definitely do not want to use 804's in a room that large - they are for medium to small rooms unless the only thing you listen to is chamber music.
You did your homework (which is refreshing- most people don't) and know that much has been written about B&W speakers. My personal opinion of them is that they are of average sound quality, but can be made to sound good by experienced set-up people. Among high volume-production speakers, I believe that the build, parts and sound quality of, say, Focal, Dynaudio and Revel are better (but sound quality is of course somewhat subjective). That said, I could see myself putting together a rock 'n roll system around the 801N, which, assuming you have the big room it needs and can afford to bi-amp, impresses it its own way. My own strong preference is for specialty (i.e., not mass-market) manufacturers like Rockport, Verity, Evolution Acoustics, Magico, etc., but that doesn't help you because they don't offer much in your price range.
Worldwide, there are an enormous number of speaker manufacturers - many hundreds - and a huge selection of choices in what appears to be your price range. You will receive dozens of recommendations in response to your question, and good advice and bad. If I were you, I would call Steve McCormack to try to draw him out on what brands of speakers he likes with your amp, given the types of music you tend to listen to, your other equipment and your room (some manufacturers refuse to endorse brands due to commercial considerations, but most will).