I have a 1990 acura integra, and would like some help.?

Ok, this is quite literally my first car. I got it when i was 17. I am current 19 about to turn 20. I've never done anything to this car, because my brother is always downing it. (he's a mechanic, and I don't know if his prejudice against my car comes from him actually knowing what he's talking about or he just doesn't like honda or any of its branch offs) Now, I would like to know if this is a car that is worth upgrading, its a 4 cylinder, 90 acura integra gs. Right now the only thing i plan on doing is puttin in a small sound system. So anybody that has an expansive knowledge about imports. I would like to hear your opinion.