I hear ya' Bob and I don't like being put in that position either.
I actually don't like to demo my stereo at all because most people expect to be blown away with a thirty second sound clip or they have already made up their mind about what it sounds like based on what it looks like or what they own. So, I just play music that I feel like listening to and I nod my head to their comments.
I always encourage people to bring or play music that they enjoy, not pick recordings that make good sound demos.
Maybe if your mystery guest really is a good guy he will enjoy listening to your personal choice of music and stick around long enough to have fun. Sometimes that happens too. 
Good luck Bob. 
My stereo is for listening to music, NOT for demo. It's not that it doesn't demo well. I'd compare it favorably any other system regardless of cost. But for me, the stereo is a means to an end, not the end itself, and that end is music reproduction. It's all about the music.
As for suggestions, Vivaldi's Four Seasons is liked by many and is not intrusive, so is the Suite from Carmen. Then your "guest" can select what they want to hear. If rock is more to your liking, then I might suggest pretty much anything from The Who - Live at Leeds. Good album, good rock, good recording. Or whatever grabs you from Pink Floyd Dark Side of the Moon.
