This is the ultimate speaker in my book at about $40K+ each (you need at least 2!):
You can spend more from companies like Wilson (Want speakers that cost 6 digits? then look at Wilson), but all that extra money is spent on the cabinet design, and I think B&W has them beat on cabinet design since mother nature designed it - its your ear canal if you didn't notice!
Here is a modern paper speaker. It is paper infused with Kevlar:
Looks kind of cool, no?
Anyway, I am still running a set of Teledyne Accoustic Research AR9's myself, with about 1000 Watts continuos power hooked up to them - bi-amped of course from 4 amplifiers. I am thinking I want a B&W upgrade, which should be a good jump, but I will be well into 5 digits if I do it for some 800's. I am still on the fence however and not in a big hurry however since the AR9's still sound pretty dang good to me!
-S