As a card-carrying audiophile with a fairly expensive dedicated 2-channel rig at home who also worked for Magnolia at Best Buy, I can speak with some considerable experience on their gear.
First, I’ve never been a fan of B&W speakers mainly because the yellow Kevlar drivers really turned me off. Having spent significant time with their new Diamond series with the silver Continuum mids I can say whatever they did has fixed the problem I had with the older drivers. I spent more time with the 804D3s than any other speaker in the store and I have to say the new 804s sound very good. I compared them directly to the 704s and I found the 804s to perform at a significantly higher level (as they damn well should for the considerable price difference) when fed with good recordings and appropriate electronics.
Ok, there’s my preamble. Now, I have to say I completely agree with @audiotroy that if 2-channel is your priority, and frankly to do full justice to the 804s, you should strongly consider either an integrated stereo amp or stereo pre/amp separates. It’s insanely easy to incorporate these seamlessly into your HT setup and be able to change between HT and pure 2-channel at the push of a button — literally two systems in one and best of both worlds.
I also agree with @erik_squires and his Anthem recommendation for an AVR, and if HT is also very important to you and it’s in your budget you can’t go wrong with Anthem. However, if HT isn’t quite as important and/or you’d rather spend less there and put the available dollars elsewhere I’d very highly recommend the Yamaha Aventage RX-A3080 that you can get from Accessoriesforless.com for $1300. I got to use all the AVRs at Magnolia with the 804s, and for whatever reason there was a special synergy between them and the Yamaha such that it was on the level with my much pricier home system. Quite frankly I was amazed at how good this combo sounded with well-recorded stereo material. Obviously the 804s will sound even better with good dedicated stereo electronics or probably an Anthem AVR driving them, but no apologies needed to be made for the music the Yammy/804s produced. I could easily make the argument, if you can’t stretch for the Anthem, to start with this combo and let things break in and give yourselves time to assess and get to know the system in your room. At that point you’ll be in a better position to judge what you might like to improve upon and/or what separate stereo components you might like to audition to improve things further.
I’ve blabbed on too long here, but you seem to be looking for some guidance and given my experience with the speakers you’re considering I thought this might be helpful. Best of luck in putting your system together.