A new headunit and door speakers will improve any system 100x than a stock unit. when you pull out the door speakers, take a look at the magnet, I guarantee they will be rated at no mroe than 100watts ( if you are lucky) So just replacing the headunit with one rated at 50x4 or 40x4 will plenty improve sound, but if you do that then you owuld want something that can handle that, like new door speakers, JL Audio make nice sets as do Pioneer or Kenwood if you need something not so high end. When it comes to amplifiers, they are not needed unless running a sub. Try running a sub, 4 door speakers off of one 200watt headunit, it will not sound as nice as it could. definitaly get an amp to run sub, one is not needed to run door speakers, unless you are just trying to run everything at a high wattage, if thats the case, go with a component set of tweeters and mids with a crossover to remove the bass from the highs.

 

i forgot to ask...you did play with all of the music control buttons right, like adjusting your bass and treble, or putting (whatever the first option is called to 3?)

 

even if he did tinker with the controls, the systems in the 3s aren't that great. i've heard them and they bothered me... hell my mazda6 with the bose system isn't that great either... and that is top of the line for mazda!

 

well i was impressed with my stock sound system, Bose has improved compared to my moms 04 maxima Bose sound but then again my first car was a Kia

 

I left my stock speakers in my Mazda6 and added a 08 sony headunit which easily amplifies the door speakers then i added a MA 12' sub with a 800 watt amp and it sounds great. wiring isnt too difficult either. and i strongly suggest making your own box for the sub because when u by them premade they use terrible wood. you gotta get the good stuff and it will sound so much better.