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.

My issue is that the room is pretty small and really and floor speakers might look a little overbearing. That being said, if there was a huge difference in the 804d vs the 805d with a sub I would have to give this some serious consideration.

Get the 804Ds They are better balanced than the 803DIs. I had 805Ns with a sub and could never get the bass to sound correct. I think you will have better bass integration with 804Ds. Besides the 804Ds & 803DIs have a way better mid-range. I was quite shocked of how 804Ds and 802DIs were very similar compared to 803DIs. Tonally speaking. The 802DIs were better than the 804Ds but 15K is a lot of money

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