First of all dont buy 4" by 6" speakers. If you dont have money and you just want some kind of sound then it ok but if you have a saw, some wire nuts, peice of wood, and a screw driver then this is what you do. Take your 4" by 6" speakers and give them to somebody you dont like because they suck. These speakers are made only to reproduce high freq sounds. Such as voice and guitar and ... you get the picture. So when your on the highway and your listening to these you hear road noise and voices. No your not crazy its your speakers well maybe your crazy. So this is where your tools and some effort come into place. Take your door panel off and if you look in the front bottom corner there is a space where there is no frame behind your door panel. So buy some 6.5 or 5.25 speakers. ( 6.5 sound much better you get better full range of sound) Also round speakers unlike 6"x9" and 4" by 6" reproduce a more realistic sound so you will get better sound quality. Take the circle patern that comes in the box with speaker and match it up to door panel where there is no frame behind it. Pencil in the circle or a little smaller than the cirlce and cut the whole in your door panel. Next buy a spacer from the local car stereo dealer or make your own with wood and black spray paint.(Easy its just a circle) Next lead your wire from the head unit to the door. ( under the dash and go into the 4" by 6" holes on the side of the car there you will find a hole that leads to the door if you have power windows. Next connect your speakers to the wire and make sure they fade left to right correctly. Then buy some dynamat at local care stereo dealer. Buy only enough to cover each door its exspensive. ( goes on the back of door panel) This will let your speaker function better and increase sound quality. You dont need it but it helps a lot. Next screw the spacer into the door and put some nuts on the back of the screws so they stay tight then screw the speaker into the spacer. I probaly missed something and spelled half the words wrong but im typing fast. There you go a way to get way better sound in your BMW 320i. Now if you got any questions on what type of speakers to buy give me an email at vball_badger@hotmail.com with the types of speakers in your area. I recomend MB Quartz there a little more expensive but sound great. I live in the Springfield Ma area so if you got more question or need help email me.