FYI you don't absolutely need that adapter, its more for if you want to continue to use the factory amp and a few of the fancier radio features such as speed volume and speaker selection (i.e. drivers seat, rear seats, all seats) To me, it's not worth the $90 that they charge for the adapter. I'd rather just install a new head unit and bypass the factory amps since an aftermarket head unit will probably have plenty of RMS power on it's own. It's up to you though.
Power in Numbers: None of us are as dumb as all of us