Will a new stereo give me better sound quality?

I recently replaced my rear stock speakers with some 250 watt sony xplod's that i put in, they sound great but my front speakers in the door cramp the style that my rear speakers have because my front speakers still crackle when the music is loud. I still have my stock stereo system in and like I said my 2 front door speakers are also stock. If I got a new CD player stereo in the dash would that improve my sound quality at all? I know different speakers give better sound but how much of a difference in sound quality will you notice with a new stereo? and also I would've replaced my stock front speakers a long time ago because they suck so bad but I removed the door panel and the door speakers are welded on. Any suggestions?