System Design with Stock Headunit

If you don't know anything about Ford's audiophile sound system you can skip down to the "Finally:" section and comment about my eqiupment list and comment on whether you think it is a good design or not.  Thanks.

I've got an 06 ford explorer with the audiophile sound system.  I want to change the 4 door speakers to MB Quart RCE 213's and PCE 213's (I happen to have a pair of each I never used.  I also wish to add a alpine 4 channel 4x100w amp.  Here are my questions:

1.  Do the RR LR RF & LF outputs on the audiophile headunit put out amplified signal or low level signal or some custom signal?  Did you know the audiophile headunit is actually an oem'd Pioneer AVIC unit.  It's got the pioneer label and AVIC model number right on the radio!!!

2.  Do the radio ouputs for each channel contain the full signal or are they less in front or more in rear?  It seems like the system is tuned with higher frequencies in the front and mid/low in the rear or the sub.  Is the factory system tuned in this way?

3.  If it is tuned, where is this done?  Headunit, amp, speakers???

4.  Is there an external amp in my 06 explorer that drives the speakers in the doors?  If so where is it located, or is there just an amp for the sub?

5.  If I want to add aftermarket speakers and amp's can I add a LOC (Line Output Converter) at the headunit (JL Audio CL441dsp, nice loc with dsp creating flat curve output and aux input for ipod).  JL Audio tells me I need to also add their summing unit to sum frequencies from front speakers + sub speakers to get full signal for external amp.  Is this true? (guess it would mean that signal is split into pieces in the headunit and needs to be recombined for full fidelity to each door.  Trying to confirm this

6.  Do I want to send full frequency signals to my new speakers? (That's the way I used to do it way back when, but now it seems things are different).

Let's say I followed JL Audio's suggestion and summed the 4 channels into the LOC then into a 4 channel alpine amp then to the door speakers.  I have the following question:

7.  How would I then get a signal to drive a sub amp?  Los pass filter xover etc?  (not real knowledgable here, need some help)

Finally:

Does this configuration make any sense? Might solve the sub out question and give me a cool looking EQ for the dash (would actually relocate the buttons below the A/C cluster and put it there!  (heated seats button right on the sides of the console, delete the pedal button as I never us it and find a place for the seat memory buttons (Yup, I'm looking to do some nice custom stuff here)

Headunit feeding:

JL Audio cl-ssi (signal combiner) combines split frequencies (JL says I need to combine frequencies out of the audiophile radio, but I'd like to confirm that here if possible.  feeding:

JL Audio cl441dsp (using dsp creates a completly flat sound curve + gives an auxiliuary input nice!!! feeding:

a Pioneer DEQ-9200 which is an auto dsp EQ which gives me digital crossover capability + tunable sub output feeding:

Front and rear channels going to an alpine 4 channel 4x100 amp feeding:

MB Quart RCE 213's in the front door and MB Quart PCE 213's in the rear doors

and finally the subwoofer output on the eq feeding a seperate amp feeding an sub driver (I'm not the thumping type, so just something better than the factory sub.

Sorry for so many questions, but I've been really researching this stuff for the past week and I've come up with a lot of things I can't seem to get answered.  I appreciate any responses I get.

Regards,

Roveer