Just out of curiosity, what's wrong with the Bose system (if you have it)? My system sounds fine and I've grown up with sound systems from the days of 8-Track and beyond. A lot of posts talk about the sound being weak but I have no problem giving myself a headache if I'm not careful.
Sound is subjective of course. Some equate power with how much they can literally "feel" the vibrations instead of hearing them. I'm a big fan of hearing the music and nothing else. In a car that's pretty hard to do, which is why I always thought it was funny when someone raved about how clean the music is on a CD. The road noise can't be eliminated, so it kind of negates that fact.
Anyway, enclosing your speakers in air-tight boxes stuffed with insulation is a good way to improve the sound production. I made some for my old Subaru years ago. The first time I heard the difference I could not believe they were the same speakers. I hardly had to use any volume adjustment at all and this was a 100 Watt system with 6 speakers.
2006 350Z Touring Coupe (5AT)
Stock for now