Well, I just make it work. I think you have to do what makes you happy, and if they can't understand that give them time. Personally, I don't think I could listen, really listen to music that is only 75db...I agree about the sub/bass issues, as they are always an issue regardless of how much concrete is in your building. I found that going to a full range speaker allowed for increased volume without the "boom" of a subwoofer. Headphones are an option, but I would not use them unless I was listening late nights. In my current arangement I share my livingroom wall with my neighbor and have people living above me...I still listen at all hours...my next-door neighbor has only complained once when I turned on my sub for an action movie.
Good luck
Good luck