HI,
nothing is going to sound worse in a good system (different thing from good components), on the contrary. Surely some recordings will sound better some mediocre, or worse, but even these ones should be enjoyable enough and far from unlistenable. When the worst recordings make sense, are easy to follow, create a believable image and sound like good music (even recorded badly), then you will get much much more from the good one. This is the only way to rediscover your music collection.