It partly depends on why a given recording sounded bad. Was it overwhelming the limitations of your system, or truly a poor recording?
A better, more revealing system will allow better recorded records to sound even better, while showing off more of the flaws in a recording. You're going to get good and bad. A lesser system tends to mask flaws.
Better systems not only will reveal more harmonic detail, but well give you a more layered and detailed soundstage, and a greater variety of dynamics, from very small to very large. You'll hear a greater difference between recordings.