I install many systems and have to say that I try to avoid Mach 460 systems at any costs. I've cut my hands up and everything trying to rewire those things. I figured that one possibly cannot get the sufficient SQ and stereo separation when the front and rear "subs" are low passed and in mono!!! If you would like a challenge, get tons of painkillers and run new wires and new full range speakers. And get a four channel amp. Those tweeters are horrible and need a replacement too. Get an amp that is 2 ohm stable per channel. If it already floats your boat, you are SOOOO lucky that the amp inputs accept such a close voltage as the Rio's outputs. Hehe... I fixed my brother's 2000 Mustang and ran all new speakers except for the rear 5x7's / 6x8's, and I added a Zapco Studio 300X on the highs and a JBL BP1200.1 driving an IDMax 12" sub.. If you ever do replace the horrible rear speakers, I recommend that you build a divide inside to separate both speakers. It didn't matter that they were in mono before, but you need better sound since the Rio is really good at that (.wav files only!!!)
I noticed the headlight sensor is reliant on the CD player and radio to be hooked up since they are in series with the circuit. No problem though... if I find which wires go to which, I'll let you know (you'll need gloces, for you'll cut your hands up in that little dash.)
Have fun and rock on with that RioCar everyone!!!