Problem with audio/sound (intermittent)

Hi
I have an intermitent problem with my 2005 9-3 18t. The symptoms are:-

Blip noise on sound system - when working
When not working no sound at all, no indicator noise but indicators work
No sat nav or phone
Only the half the info on the SID display available when its playing up
Alarm and horn work ok - no problem with lights or door openings. No problem with ignition key.

I think it is the BUS 0 or EHU but have been told by a SAAB garage (over the phone) that it is the CIM and have quoted a hefty price - my gut feeling is it is not the CIM.

I look forward to hearing from you.

Thanks

Len