1 and 4 are not that interesting since are definitive. You like certain sound character, you like it, done, nothing to discuss further. If you want accurate reproduction you have to rely on third party or your own measurements since you wont have a reference, as SpinyNorman pointed out.
But I find 2 and 3 interesting.
How can hi-fi gear make recordings better? I'm not talking going for vinyl against CD because they will be two different mastering recordings, which is apples to oranges. How does the system itself make bad recordings sound better with the same media and with the same mastering? Your experiences.