OP,
You needn’t know what characteristic you want to improve. This typically simply means you like all aspects of your current sound. That is a good thing.
I have been improving the sound of my system continually for fifty years. Many times, I have simply wanted all aspects to improve… dynamics, detail, soundstage, sound floor… etc. Moving to better equipment will do that. Once you have one piece of much better equipment, then upgrading others to that new level is likely to follow. Hopefully, falling on a great and higher plateau you are happy on for a long time.
Occationally an upgrade will move your system a bit too far in one or more aspects. Then you will have reason to change some particular aspects… could be tonal balance, too harshly revealing… more bass… who knows.