I guess a more general question might be are speakers today (>$15k) better than their 25 year old equivalents?
Some are, some aren't. I still use older speakers - Wilson, and Vandersteen and ML CLS that perform very well and I have heard and respect original Quads within their limitations. Very hard to assess speakers at a dealer in a totally different system than yours and be sure they will sound better. The speakers you have are very good and it would be rolling very expensive dice to shell out for something that sounded good to you on the mainland in a totally different room and system. Hope you make the right decision though.