sound/hifi in omega b what can you do?

Hallöchen, don’t have a problem (more or less) but a question about the hifi in omega b… somehow I have the need to do something about it, so far it’s all series, should be called ccr600 with 6x cd-changer..all original opel and doesn’t sound bad at all…..but no matter, which is hard to wonder, when I saw the speakers I almost fell on the back…that’s not possible at all are my buddy and I with too much optimismu …and we’ve got a lot of optimism and we’ve got a lot of door covering and so on and we still thought “can’t be so hard” DENKST DE!!!! can now explain to me here how the sound system in the omega b is built……and what you can build in??????? planned were new speakers in the doors in front and back, another radio and a half-ventile de-pressor… the most important would be speakers and de-pressors….how can you where best? cable for the detachment installed?? actually wanted to install new caps for the new loudspeakers…but I can probably forget that… effort would be too big I think…or does someone have a tip? by the way I like good sound from a ventilated system, so with cheap on make up with subwoofer and detachment I don’t stand! but it should still be affordable and without all too big work to build up…. would be great if you would just tell me what I’m doing k ann, or what you might have done already and what brings…and it should stay in the normal range, so no super highend expansion for a hit search I have already tried..but unfortunately no found thanks mfg alex