Wiring after market stereo installation

[Hookoo3]

I just replaced my CDR-220 with a new (no name brand) after market double din,CD, Ipod/ GPS system. After considerable time I have been able to get the dash and door speakers to work through the Porsche M490 amp (4x40). I'm not sure if I have a grounding issue as every time I change volume or mode I get a very loud sound indicating the change. Is this normal to have an indicator sound?

My second question is how to wire up the rear speakers. With the CDR-220 I was able to connect the rear speakers to the Head Unit and the dash and doors ran off the amp. I do have the wiring diagrams for the Porsche amp, CDR-220 and the new player however I have no idea how to add the rear speakers. I was able to connect the new GPS player to the amp with the 4 speaker out connections and grounds. The new GPS player also has 2 sets of RCA out connectors labelled for front and rear however they do not power the rear speakers. Whats the best way to wire in the rear speakers using the head unit and the 4x40 Porsche amp? Should I connect the rca connectors to the amp and use the other speaker outs on the head unit for the rear speakers? At this time I'm not really interested in adding another amp and would like to use the current setup. Thanks in advance for any help.

2001 Boxster S

Hookoo3

[Ross1]

By connecting the "speaker out" from your head unit to the amp, you have fed an amplified signal into an amplifier! This is what's causing your noise problem. You have answered your own question. The "rca outs" need to be fed to the amp and the rear speakers to the rear "speaker out" off the head unit. This will allow you to use the fade control for balance. This would mimic the configuration of the CDR-220.

[Hookoo3]

That's just the clarification I was looking for. Thanks.