The only electronic changes have been to the protection circuits so it is now more difficult to burn out the tweeters in particular. The same mod was done to all the active speakers at that time.
The 8000 woofers (!) were also changed slightly on the 8000's. The dust cone want from convex to concave.
I have had loads of pairs of 8000's and to my ears there are no sonic differences!!!!
Upgrade components are supplied with all replacement tweeters.