bmw series 3 sound upgrade

Hi, im having problems upgradin the audio sistem, first in the vehicle information database tells me that the original radio is din size, second the front speakers are a three way system, not two like the database says, and the rear speakers are 6 1/2 not 5 1/4, i´d like to know the metra code for this car because it´s larger than a din, dos this car have an external amplifire?, i´m planning to install an alpine 7995 source unit, one subwoofer (power hx2 12) two punch amps, and i don´t know the size of the three way sistem wich i want to remove to put a better one, i was thinking on dynaudio or dls do you have any ideas?? the other side of the history is if i leave the original radio and install everything else, do you thig this could improve the sistem, do you have the wirin diagram, please tell me somthing, i don´t know what to do.

thanks!

What year and which 3 series ( 318, 320,325 ?? ).

• If you need speaker information go here : http://www.americaninternational.net
• If you need wiring harness go here : http://www.metraonline.com/productcatalog.htm