$200 well spent / Happy ears
A few years ago I replaced my stock stereo with am Alpine DVD/NAV unit. Sound was better, but still sucked. Then a couple years ago I put a small powered sub behind the rear seat. Sound still sucked, but at last I had so some lows.
For Christmas my wife bought me Polk speakers. DB6501 6.5" components for the front and DB651 6.5" for the rear. Along with the adapter plates, it was all under $200 from Ebay. I just finished installing it all. Money well spent!! I finally have a respectable sounding stereo! If you've still got those crappy stock speakers, ditch em. They are horrible. I finally have the highs I've been missing and can turn up the volume to an enjoyable level without distortion.
Like many of the guys on the forum, I drilled the 2" holes and flush mounted the tweeters in three door just above the black panel where the window switches are. Looks slick and sounds great!