As you can see from most of the responses, Natalie is right,"the size of your room dictates "which model you should use. B&W even say that the N804 is for small to medium size rooms, while the N803 is for medium size rooms. At 11'X13', my room is small, with 24" behind my speakers and a foot behind my head, I am right at 9' from my N804s. I have all the bass I want or need. Power is BelCanto EVo 200.2 through a Cary SLP 2002 preamp.
I think your N804s are all you need for your room size. These speakers need at least 300 hours to breakin. They will improve up to 500 hours according to many posts I have read. If you need more bass, add a sub , REL comes to mind.
claud