The first time I ever heard a system was in a friends quickly and badly set up car. There was a lot of hiss from the trebles. Yet when the 15" parcel mounted sub kicked in my mind was blown and changed forever. I had no idea anything like this was possible in a car. To this day even this terrible instal amazed me more than anything since. Listening to much better systems is great of course. But nothing compares to going from nothing at all to the shock of your first sub BOOM!
The first time I fired up my own system in the mid nineties was quite an amazing time. Feeling the bass effortlessly flow through me was a lot of fun. I spent that whole summer cruising around, grinning like mad. This was a golden age. Young enough to feel like a kid with no responsibilities, but old enough to have freedom, great audio toys and fun with girls. What a great time

The first time I went to a high end car audio shop was a real eye opener. I saw and heard Dynaudio, Phoenix Gold ZPA amps, JL W6 subs, a whole world of high end candy. I suddenly realised how poor I felt. Lots of saving up to do!
Ps
Lots of my systems got progressively better sounding, but also smaller and more sensible. Sometimes I think going back to the older systems might be more fun.