I think one of the overall compromises on the Advents was the tweeter. Back in the day tweeters that went low enough to mate with the Advent woofers were, at best, rare. The tweeter listed by
@THD+N is impressive in its low end extension and fs though the crossover may need to be tweaked. There are other options for the NLA. Some love the Advent tweeter but considering how many of these get the Econowave treatment it is obvious others disagree.
If you're interested Classic Speaker pages has a dedicated Advent section, though CSP doesn't get as much traffic as AK.
http://classicspeakerpages.net/
Also, despite what is listed on the back of the speaker, i.e. 8 ohm, these are not 8 ohm speakers. In my experience running them on amplification not rated down to at least 6 ohms will eventually burn out the amplifier. YMMV.