How different between B&W 804s & B&W 805s????

I'd save the money..but then again, I am not a BW fan

I have heard the MC6900 driving both and it is a good match either way you go. Both the 804 and 805 are nice speakers. There is something to be said for the two way design and I would not agree that 3 way floorstanders are always better than bookshelves. That is not to say that I recomend not getting the 804. You said you already have the 805 but I would A/B the 804 and 805 at a store carrying both. Audio "memory" is very short lived any other comparison (listening to the 805 at home and the 804 at a vendor) is not coing to help. Also, by listening to both in the same space you will at least have the same acoustic environment in which to make the comparison. Listen to them driven by a mcintosh amp. Keep listening - more than one session - until you know the answer.

The 804s tonal balance is a little brighter and tighter sounding than the 805s. Many have commented on the 804s being a little bass shy but I found a good quality, high current capable amp should alleviate that issue. The 804s do respond well to high quality components. In comparison the 805s sound is a little more rounded and even handed with its well balanced coherence. Depending on your room acoustics the 805 with a sub might be more flexible and pleasing with its greater bass impact. Otherwise the 804s is a good choice if you prefer a two box solution.

Do you have a dedicated room? If you do, what is the size of the room?

The 805s sounds ok to me until one day i heard it driven by a McIntosh 6900, i realize this is what my speakers need and i'm saving money for this amp now. I can't stop thinking about it :-).
You guys so lucky living in U.S where you can borrow amp, cdp bring home and testing with your system. NOT LIKE MY COUNTRY. Thanks you so much for your advices... I also like the 804s. Its second hand but few months used only. The importand thing is it's a nice price. My room size is only 12sqm(3mx4m. Btw does anyone here using NORDOST interconnect, speakers cable with B&W??? How's the result???