There are three basic systems
1) the stereo or base if you read the history only a few unlucky people in the US got this one in the 2010 early 2011 year. but its standard world wide and you pay for the other 2 system in other country's even Canada
2)The Hi Fi 6 amped channels and 10 speakers
analog 5 volt differential from the HU to the amp 4 channels
3)The L7 or top Hi Fi 9 channels 13 speakers I think check
the pdf surround sound and the bad, a fiberoptic proprietary
connection between the HU and amp.
The Hi Fi is the easiest to modify as a result.
If you read the history in those links I sent in the previous response it describes everything in detail.
In the front for Hi Fi, two channels go to the doors and two to the floors.
If you have the right Technic harness it will have 6 channels
out 4 in . It should be a real short one as there is already wiring to the the trunk and most people put there amp in the OEM location.