Thanks to geeman, we spent today measuring exactly what goes on in the 2003.5 sedan's Bose system.
Couple of points (see pics on
http://kward1.homestead.com/G35pics.html but 56k, forget it):
1)The door speakers in this car are NOT 2 ohm! They are 4 ohm and as such can be replaced with new aftermarket speakers IF you want them to play severely eq'd sound. (See pics)
2) The system doesn't measure as having sub-bass. Has a peak at 50 and drops hard below that. Also rolls off at about a 6dB/octave slope from 50 Hz all the way to 20K. Not flat at all - tilts.
The front door speakers start rolling off at about 65 Hz, with a bump from 65 to 100 Hz. They have a wide happy-face trough from about 120 Hz to about 10k, with a narrow spike EQ'd in at about 800.
3) The rear speakers are rolled off at about 120 Hz. They also have a wide trough and narrow spike, and the highs roll off too above 10k.
4) The sub seems to play 80 Hz and down, with like a 25-30 Hz highpass subsonic filter.
5) The HU output is flat (minus negligible auto-loudness at the bottom end of the volume range) and decent in output voltage. At full output no clipping of a 1kHz sine wave was observed.
SO bottom line is that the output of the Bose amp is a roller-coaster, sonically speaking, but the preouts are good quality.
As far as LOCs go, I'd try an amp with balanced inputs (DLS, xtant, JL) and not even USE a GLI. I'd expect amps that can't take balanced in (Diamond, for one) to be noisy as heck.