Here's what I've learned about the factory Inifinity system:
Head Unit: attaches to amp via black 6-pin DIN cable (4 channels, pwr, gnd). MITAH and MITSRCVR adapters will change this 6-pin DIN cable into four (front L/R and rear L/R) RCA plugs and a "turn on lead" to go into after market amps. You'll likely also need LVT (low volt trigger) for other amps to signal power on.
Amp: Inputs: 6-pin DIN (4 channels, power and grnd)
Outputs: unknown specs, likely 100W/channel, attaches to speakers via white harness.
THE STOCK INFINITY AMP HAS HI PASS FILTERS FOR FRONT DASH TWEETERS AND LOW PASS FILTERS FOR FRONT DOORS BUILT IN!
Therefore, front door speakers are only mid/bass, with no highs. Keep your front dash tweeters if you use the stock amp and want highs up front. New tweeters (if yours are spent like mine) can be retrofit into covers if they are small (neo tweeters):
http://www.dsmtuners.com/forums/arti...-speakers.html
You can use wiring harness/adapter 70-7001 to create free wire ends for your speaker connections for an after market amp hookup. 70-7001 just plugs into your stock speaker wires' original white amp harness. You can do without the 70-7001 by just cutting the wires off the original amp harness/plug. <Do not confuse with 71-7001 (which creates new speaker wire hookups from stock amp)>
note: MITAH from installer.com also includes speaker wiring harness/adapter (70-7001). Other sellers (such as hifisoundconnection.com) do not inlcude this adapter in their MITAH adapter (MITSRCVR only)
Hope this helps somebody. It took me a while to piece it all together.