A stereo system sounds good when the experience of listening is about enjoying the music and not fretting about how the sound compares to some absolute audiophile standard.
In my experience, listeners can achieve this by choosing their main system components and speakers to achieve the type of sound they most enjoy with the music they most enjoy listening to. Cables and tweaks will not get you there if the main components and speakers are not aligned toward your preferences. Once I figured out that tone and dynamics are most important to my listening enjoyment, then putting together a satisfying system became much easier.