Brian & Bluebell,
First of all, the N802 and N804 have been eliminated in the new line up. By adding another bass driver to the 803, changing the crossover, reinforcing the cabinet and adding the new tweeter the new 803D will outperform the existing 802 so they eliminated the 802. Basically, B&W made a marketing decision to offer fewer options in the Nautilus-Diamond line and to substantially increase their profit margins. The way they justify this is by radically and substantially improving the performance of the remaining speakers in the line.
Forget about how good the Sig 805's sound. Many people were thinking that the new nautilus line would just incorporate the Signature tweeter and crossover on the older 804's, 803's and 802's. NO!! In order to justify the huge price increases (the new 803D will retail for around $8,000) B&W
has (can you believe this) significantly improved upon the sound of the Signature tweeter. The new diamond tweeter smokes the Signature tweeter. Additionally, the crossover has been reworked and the internal cabinet structure redesigined.
So B&W's goal was to offer owners of the new diamond series a product that surpasses the performance of the Sig 805's...which makes sense whne you consider the price difference.
B&W has perfected the art of making sure as you move up in their line each speaker has a noticeable improvment. They're one of the best compnaies I've seen at doing that. If you line up and listen to the new 705, N805 and Sig 805's (ab'ing all three..I've done that) you can hear the improvments as you go up. And the differences are not subtle. B&W has done that again with teh new diamond series.
I'm excited to hear the diamond line. All of the information I gave you above was provided from a reliable source who is a B&W insider.
Good luck!
AVGURU