I have found these changes in my humble journey (not in any particular order):
1. Speakers disappearing
2. Improved colors for different instruments
3. Instead of your brain interpreting the feel of what an instrument is made from - brass, wood, pig-skin - the rig imparts the info.
4. Removal of congestion when the music got busy
5. Increased stage depth - instruments hang in space
6. Improvement in fine inner detail. e.g. a tiny cough or comment in the audience, shimmer of a brushed cymbal, rosin puffing off a bow, a smile on the vocalist’s face...
7. Minute changes to system easily heard.
8. All recordings sound great, even damaged vinyl.