In my opinion u shud change d speakers first. Reason is now a days most of cars coming with usb input so d source will b same (mp3) whether u play on stock hu or aftermarket, d quality will not differ much unless u go for audiophile HU means u buy new HU but u will feel not much difference in quality

U shud change speakers cz stock spk r made of paper cones n usually come without tweeters. At louder volumes sound will start to distort n in few months cone will rupture. Aftermarket spk will sound much much better especially components with stock HU using usb or CD.

This post has been edited by mughal90: Nov 18 2012, 07:40 AM

All debates aside bro.....since u r using fm modulator for usb u should get HEADUNIT FIRST cz no matter how xpensive spk u get they will sound crap with fm modulator Headunit first followed shortly by spk.