Michaelkingdom, I always found your posts helpful as I went on my own speaker journey. I share your appreciation for the original B&W 805 - I had a pair in the Natural Cherry and then upgraded to the 805 Signature. I sold those to fund a new business venture, but always regretted letting them go. I LOVED those speakers, and still think the 805 Sigs are some of the most beautiful ever.
I did a write-up earlier this year after spending time listening to the D2 vs. D3 in the same showroom, on the same equipment, in the same position. From what my ears heard, the smart play was to grab the D2 on closeout. Of the three of us in the room, my wife preferred the D3 but the sales rep and I both liked the D2.
I've also heard the 805D, but in a comparison against the WB Arcs, and I ended up with the Arcs (much smoother, sweeter, and more open). Problem is, though I've heard them all, including 804 and 802, I've never heard the D3 in the same room and same time as an original N or S series. So that specific comparison is one I can only offer from putting together listening impressions at different times in different places.
I know some people speak of the D3 as a dramatically upgraded speaker, but I just didn't hear that. Different yes, earth-shattering no, but listening impressions are so personal. If you said you had $7K burning a hole in your pocket, I wouldn't dissuade you from getting some new D3 - I think they're super-sexy in white. But given how much you love the original, and I share that, it's a large cost difference between the two. By my math, new D3 will run you a good $4500 more than a nice-condition pre-owned set of 805S. You could also go the Wilson Benesch route (which from my online research is a path many 805 owners have taken), but that's a discussion for a different day if you're so inclined.
Given how much you like the original but disliked the 805D, I'd say that if you can't compare the N/S vs. D3 in your space, at the same time, on the same equipment, I think it's a dicey upgrade for you.