Upgrading soundsystem, could need som tips

[nitrox111]

Edited:

Hi, just bought a BMW E70 with the Hamann Flash bodykit and the car is awsome, but i realy need something to boost the audio up.

I got the CCC navi, speakers in 4 doors and no tweeters.. i think there might be some small subs under the front seats

I couldnt find any amplifier where google told me it was supposed to be (picture), so i guess that means i got the base audio system..

At Bavsound.com there is no option for PnP amp, so question now is how can i upgrade my audio-system when i dont have an amplifier..
Someone said i couldnt use Hi/Lo-filter either because it was hardcoded or something..