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

If it were me I would wait until I could get the 803's. The 805's with a sub is a good combo. Personally I think you may be disappointed in going to the 804's IF you have give up the sub. With the 803's you may not even want the sub.
Just my opinion.

Ok the room will make a big difference. My experience is monitors with a sub should work out better. That being said my room is 12' X 26' with the speakers on the long wall (I have no other choice). I used to really like B&W until I heard the Dynaudio's. I own the C1's with a Rel B3 sub and wanted to upgrade to the C2's. So my dealer loaned me his C2's for a week. What I found the C2's was a wall of sound. Not bad but I really prefer the monitors in my setup. Now at the dealer he has a much bigger room and the C2's just blow away the C1's.

Just my experience with my room

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.

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.

Budt
I got the Dyns 1 year ago next month.

Jdec
Interesting. The dealer I went to told me the entire 800 series had switched to the diamond series when I was searching and there was no difference in the way they looked. They also told me that all the drivers had been upgraded not just the tweeters. I may have been misinformed. I didn't know any better and they were the only brick and mortar dealer I refuse to buy anything from them because of their attitude.

Just found my B&W brochure and you are right. Both the 804 and 805 did not have the diamond tweeter at the time I listened to them. Also at the time I thought floorstanders would work in my room and was more interested on the 802 and 803's which is why I didn't ask more questions regarding the 804 and 805's.

Thank you for correcting me