Well, the worst ones in a home stereo system are almost always the real crappy cheap ones that have come in compact stereo systems from the likes of Aiwa, TEchnics, Soundesign, Sanyo, Panasonic, Sony, Fisher, and the others for years that are cheap and mass produced.
The worst ones I have heard that were very expensive and should have sounded good were Peak Consults at Sound By Singer in NYC a few years back. All bass high end, no midrange. Something must have been wrong with the setup somewhere, yet this mega buck system was demoed as if normal. I've never heard Peak Consults otherwise so hard to say for sure. Maybe it was fine and there is someone out there that would take to the flavor of the sound, which admittedly was quite different from most anything else I have ever heard.
I've also heard some large Sonus Fabers sound really bad run off Krell amps in an old shop in Paramus NJ a few years back, but I know that was an aberration in that I have heard the same SFs sound very nice elsewhere set up right.
