it depends on the quality of speaker you buy if the sq is noticeable. the factory tweeters are very small. you wouldnt be able to replace them without some dash modification. I put my tweeters in a new location and just left the stock ones unhooked and in their original location.

 

Always components up front. Coax will be worse than factory. The tweeters are worth the effort. You can get 3/4" tweeters to fit in the factory locations.