I don't know a ton about Advent, but I know it was started by Henry Kloss, who was a very well respected audio designer. That sounds like it may have been towards the end of his stint there, but when he was designing those speakers, they were considered to be very, very good.
A lot of people talk about stacking 2 sets of them - the top one upside down. This sounds goofy to me, but some vintage nuts claim it just sounds awesome. I won't judge until I hear it.
I'd say you've probably got yourself a pretty nice pair of speakers... if they were designed by Kloss, then they might even have some vintage collector's appeal as well.
