[GuidoK]

1. Have you actually looked at if your amp uses the coax cable with the amp?
Most DSP amps don't use the coax input. Afaik all DSP amps have the physical input, but if its not used, it also doesnt work. My guess its programmable to use or not (probably with ncs expert).
If the coax imput is used, its afaik only used with the CD, as the coax runs from cd changer to amp (the headunit doesnt have coax out).
For the rest the amp has normal line inputs. you can look up the wiring in WDS.
I think DSP amps in cars without nav mostly use the coax input.
2. the biggest issue is not to use coax/dsp input, but having your amp switched on when the HU also switches on. The amp gets a signal to turn on. I dont know if this is via Ibus/Kbus or if its a dedicated hi/low line as used in aftermarket amps.