Hi, my experience might be of some help if you want to upgrade the 803D2, which is what I've done. I did buy a new set of Sonus Faber Olympica III, and wanted so much to replace my 803 (or to be honest, my wife wanted to replace my 803...) The SF midrange was to die for, but the same cannot be said about the tweeter and bass. To make a long story short, I sold the SF after upgrading the X-over in the 803.
The 803 suffers from; some light upper frequency enhancement with the tweeter, and some nasality and "in the box" sound from the Kevlar midrange.
When going through the x-over (B&W had kindly posted the schematic on their homepage), it was obvious that the 47uF MKP Mundorf and the industrial resistor in series with the midrange was a week point. I knew also that the 5,1uF Mundorf Supreme SGO combined with tweeters easily can highlight the upper frequencies, too much in a not optimal set up.
I first replaced the 47uF with the new EVO MCap Alu oil and put in a Duelund Silver CAST resistor. I also replaced the 10uF Supreme Oil in parallel with Supreme SGO.
It took some hundred hours to burn in the new setup, but the result was very satisfying. In brief, a much larger soundstage, the in the box sound was 75% reduced, the bass(!) was indeed punchier, 3D stage in all direction had grown. At the same time, there were some highlighting of the upper midrange that was not to my likings. I therefore decided to replace the EVO MCap with the new Supreme EVO Oil.
At the same time I decided to replace the 5,1uF with a Duelund Copper CAST to see if I could get more from the tweeter.
It now needed some 500 hours to sound OK, and after around 700hours, it was confirmed, not only was the midrange free from any kind of boxiness, it was also the best sounding midrange I've experienced so far in my home. The tweeter together with the midrange now sounds like a Stradivarius with all I can wish for regarding holography and texture.
I have listened to the new 805D3 in two different setups. The first did impress me deeply. They had the speed and holography like never before. In the second set up they did not impress me at all, just telling me that the surrounding is just as important as the speaker themselves. I did like the speed and holography, but they did not have the texture as the 803 now has.
With the speed from the 805 in mind, I decided to replace the MKP for the bass drivers as well, this time with the fantastic resistors from Pathaudio and Mundorf EVO Alu in oil.
This time the upgrade gave me some more macro dynamic, but not as much as I had hoped for. It seems like the driver themselves are the bottleneck here.
There is space for the upgrade behind the Kevlar driver, but you have to reorganize X-over a bit. For those how want to see how it can be done, just send me a mail, s-b-o@frisurf.no.
I'm very happy I sold the Sonus, the sound from the 803 betters them in every aspect, and this with a great margin. I've of course considered the new 804D3, but I'm not sure they will better the fantastic texture, bass and resolution from the 803. Be aware, they use MKP, electrolyte and not the top of the line Mundorf capacitors. They have also started to bypass the capacitors with smaller values. I've never succeeded with this little trick in my x-overs, for power supplies, yes, but not in loudspeakers.
The 803D3 are too expensive, and since I've now started to upgrade of the 803, I've ordered the new Continuum drivers to replace the Kevlar. Still waiting for the drivers to arrive.
My experience tells me, there is lot more to get from the 803 with better components, and it is a shame that B&W has not offered a signature model with these upgrades incorporated already!
(To bad I cannot show any photoes here in the Forum)