If you can swing it I always recommend going to an audio show if you want to get a sense of where your system falls in the range of sound quality. In your case I think you will be pleasantly surprised. Your speakers don't reproduce the deepest bass or go extremely loud but they sound very good at typical listening levels.
I've got "vintage" components as well (Thiel CS6, Krell KSA 300S, KRC-2) and I figured that new state of the art gear would blow my system away until I went to AXPONA a few years ago. Turns out that my system holds it's own against most of the six-figure systems I heard.
If you've got an upgrade itch I suggest you start with getting a subwoofer. This will make a big difference and you don't have to spend huge bucks to get a sub that will do a nice job.