05-17-2011, 04:43 AM
Join Date: Mar 2003
Mein Auto: S54 M Coupe x2, M52 Z3
What you need to do is find some cheap crossovers on ebay and then pick up a 2 or 4 channel amp for the speakers.
I have to ask what speakers you upgraded to, as they should have come with crossovers and they should NOT be compatible with the factory amp.
The factory head unit is a pre-amp only setup, and requires an amp to function, so you really can't run the rear channels off the head unit, so you can nix that idea.
Personally, I think the factory head unit sounds just fine, the only downside is that some people complain about skipping, I don't have a skipping problem, but the roads in Florida are excellent and dramatically lacking potholes.
So you can go a few ways...
1) Get a 2 channel amp to run your front speakers and keep the mono sub amp you already have. (what my friend Mark is doing)
2) Get a 4 channel amp to run your front speakers and use the rear 2 channels bridged for the sub (what I am currently doing in the wife's car)
3) Get a 5 channel amp to run all 4 speakers and a sub (what I am doing in the SG)
4) Get a 4 channel amp to run all 4 speakers and add mono amp for the rear sub (what I am doing in the EB)
My friend Mark went with a 2 channel amp that was rather small. Here is a pic installed in the factory location.
2001 Alpine / Schwartz Coupe
2001 Estoril / Estoril Coupe
2001 Steel Grey / Estoril Coupe
1999 Estoril / Estoril Coupe
Sunroofs are for girls.