My speakers are also the oldest piece in my rig but I have finally decided to upgrade them. I've been using Martin Logan Odyssey's for the last 5-6 years and have been mighty happy with them but am stepping up(I hope!) to the new LS9's but not the ones from AV123 but custom from Denny at Custom Concepts. I'm excited about hearing them, I think they're going to be beasts though.
I've upgraded everything in my system with the exception of the speakers, and like you, have enjoyed hearing each improvement. I think upgrading to the Cary SLP98P was the biggest difference so far. Now we'll see how big of an upgrade the new speakers are......or I hope they are anyway!!
John