I never heard of any kit that allows you to interface with the DSP amp. You can connect to the regular amp as it can accept audio input from your head unit. The DSP amp is totally different. It won't even turn on without the Business CD and MID connected. I just installed the Pioneer AVIC-Z1 in my X5 with DSP amp. I had to disconnect the amp and directly wired the head unit to the speakers (via the speaker wires that were connected to the amp).

Make sure your installer understands that you have the DSP amp. As a matter of fact, why don't you test his knowledge and ask him what is the difference between the regular amp and the DSP amp, if he doesn't know, take your car somewhere else.

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[Sold] 2004 X5 4.4i - Sterling Gray - Truffle Brown, Sport, Preminum, Rear Climate, DSP, Sirius, PDC, 132's (19 inch wheel), Comfort Seats
Dynavin, JL Audio Stealthbox, Alpine PDX-5 Amp