I previously owned the 804S before upgrading to the 803D. Unfortunately I haven't directly compared them to the 805S, so cannot comment on 804S vs 805S.
But I do want to comment on the 804S and 803D given some of the posts above.
The 804S is a very open (definitely not congested or boxy) high definition loudspeaker that remains composed at surprisingly high volumes. While it performed well on modest Marantz gear (SR9300, PS17SA, SM17SA), the overall tonal balance was a light in my large open plan lounge.
The 803D is all round improvement (midrange a bit more laid back than the 804S), but much better bass and tonal balance. And contrary to a post above, the driver integration is superb and noticeably better than the 804S which was not bad. Surprisingly the 803D is not as demanding on amplification as the 804S, but does responds to every improvement up the chain.
I did try the 804S in a small room (3m x 3.5m) where the bass tonal balance was good, if not earth moving.
My suggestion is to compare the 804S to 803S to 805S+subwoofer with your preferred amplification before making a decision.
BTW, the Marantz PM14Mk2 is a great amp and will drive the 804S or 803S/D fine.