BMW DSP audio systems...

[off_again]

Mmm, my recently aquired 535 is loverly but the sound system is a little crap to say the least. I do have a rather good Pioneer head unit which was earmarked to replace the standard Business RDS system, only to discover I also have the DSP amp in the boot (and no CD changer - bugger!).

Now, not sure if anyone knows about this but I have a couple of questions:

1) Can the headunit be replaced with something else which has RCA pre-amp connectors - is there anything else I need to connect this to the DSP system?

2) What is the best way of boosting what I already have? Bass is well down and would like to have it improved (then again I am only using tapes ?!?!? or radio so not a good start!

3) Would like to get a CD changer - but which ones are compatible with the DSP system. From what I understand it has a direct connector from the CD changer to the DSP amp, which differs from those which dont have the DSP - which goes to the headunit. Is the standard CD changer the same for both non-DSP and DSP systems? Plenty on eBay I could pick up....

4) I have full telephone preparation but a missing phone. Anyone know where to get one or how to replace what I already have? There doesnt seem to be much info on the web....

Thanks in advance...

[off_again]

Its a 97 model on a P plate....