I also have 805 signature (since sept 03) and I have the same questions than you. I would be interrested to know what you have done since (subwoofer or 802N or others).
I love the warm transparent medium of the 805 sign, and when I wanted to upgrade to 802, I found all better in 802 (bass, treebles, soundstage 3D enhanced etc...but but but...less transparency on the voices!
O the magic medium of the 805 signatures!
I could not take 802 cause the high medium of 802 (or the junction with tweeter I don't know exactly) is a little bright, and tiring when like me you ear 3 hours of musique every evening :-)
Now I wonder which subwoofer I can buy.
I tried ASW 800, but makes vibrate my floor, even at normal volume (I think that frenquencies between 16 and 35 Hz are doing mechanical vibration in the room).
So I am thinking of using a Velodyne DD 10 because it is very adjustable to the room (many parameters/ micro/ response curve displayable and adjustable/ sub-bass can be cut... etc).
I have seen that nice Audiogon fews have adviced you A REL.
What have you tried?
What would you recommend? REL or Velodyne DD? or other?
I think also that some amplifier could compensate (add bass). I have never tried Cayin 500 on 805 sig, but listen to it on 802, and it has twice bass than with a chord 2600.
I am also thinking of plinius 9200, because cayin 500 does not provide pre-out to connect subwoofers, in case cayin valve amplifier does not compensate enough the lack of bass of 805 monitors.
About cables, do you have recommendations? I have old big monsters. not even biwired :-)
Tried Ecosse cables, all was nicer except the level of treeble: too much compared to the level of the voices.
I would be glad to read what you have done, and what you recommend.