Replacing Amp

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I have a 1998 with the 590 radio option (dash and door speakers) with the CDR-210. I purchased a rear speaker set from PNP. I wanted to wire it directly into the amp, so I found a 6x40 factory amp on ebay out of a 911. In this a plug and play type of replacement? I have the additional cable and wiring instructions for the rear speakers.

I am also thinking of trying to find a CDR-220 to keep the factory look, but add the ability to plug the ipod in directly. Has anyone done this, or do you just go with an aftermarket? If I go aftermarket, can I use the existing amp and wiring?

Thanks!