Should I buy the B&W 804d's or 805d's

When I liked B&W I compared the 805d to the 804d 803d and 802d's. Thats why I first recommended 803d's. When I did demo them they in at the dealer in a 20' 30' room. Also when I listened to the 805's they did not have a sub connected. So my personal opinion the 805s with a sub would be what I would recommend based on my experiences in your room.

Ideally you should demo them in your room with your electronics if at all possible. Everyone has their own opinion of whats sounds best.

Xti16, how would you compare the 805Diamond's to the C1's in overall terms.

The 805D's are the best B&W speakers I have ever heard, thats including their top of the line speaker, if you like B&W.

Personally the C1's with the esotar2 tweeter is so much smoother compared to the B&W diamonds (not as bright). The mid range sounds faster and a world more natural (especially acoustic guitars) and not as forward. Low end is very close but I think the C1's had a tad more punch. Overall the C1's to me sound more balanced from top to bottom. The C1's are more expensive with the stands which you really need ($7000 + $450). I also prefer the construction of the C1's too. The C1's have a 3" voice coil and made with HDF instead of MDF. I also feel the C1's have a better sound stage and more depth.

When I was on my speaker search I listened to the B&Ws first followed by the Sonus faber line. To me I prefered the SF's over B&W but was just a tad too much laid back. When I heard the C1's I had to have them right then. My search was over.

Xti16
Your post is rather misleading. According to your other posts you bought the Dynaudio C1's long ago.So there is no way you compared the 805D to them since it wasn't released till just recently( atleast 2 years later than what you claim).