Wish I could, but seem to have lost all that stuff.
What I did was print out the amp wiring diagram from the service manual pdf in the below links, then googled the HU and printed that out too.

I then made a 3rd document showing pins/colors from the HU to the Amp wires and dove in.

 

2v is pretty low but it can work, you have to turn it allllll the way up though. I did the 4 channel mod and ran my front pre outs down to the amp and the sub pre outs down as well. For my alpine I have subs set to +15 volume and I have the cross over set to 80 on the fronts to cut out some bass in the doors. Sound quality is great and it still vibrates your *** and mirrors when the subs are in their sweet range frequency wise. Volume is usually between 3/4 and full for me. I have been wanting to see if I can get the speed sensing function to work in the coupe, just a tad bit more volume with my current setup would be perfect for my ears. Most iTunes material is fine, pandora etc are slightly lower on output so you can't quite blast it.

 

The problem with that is it isnt volume. Its gain if it's from the deck. Volume is "Level" on the amp. You have to be extremely careful adjusting gain to max on the deck or amp, you will eventually start clipping.

 

We need to know specifics on your setup to tell you exactly what to do with what you have.

To start, You should have a harness that came with the alpine unit. (Little black square plug with a bunch of wires coming out of it) As stated in my earlier post you need to look at page 50 of your manual for the wire diagram. The white-black / white pair and the grey / grey-black pair are for your front L/R speakers.

In a typical setup you would have been given another harness that plugs into the stock one that is wired in the car. You wire the alpine harness to this conversion harness so that you can utilize the existing wiring of the stock unit. The conversion harness is not going to use the same color wires as the alpine provided one. You need to look at the diagram for the conversion harness to find out which wires are for the front L/R speakers. Once you find those you wire the white-black/white wires up and gray/gray-black wires up to them.

(These are most likely the wires you currently have the pre outs hooked to)

 

You are correct, the setting on the alpine unit is called "subwoofer volume" I believe. At 2v the subs are doing nothing basically. Without cranking that up you barely hear them. I swapped between the rear pre outs and the sub outs on the deck with the fader set full rear to see what the difference was, nothing too noticeable and with the amps built in cross over using the sub pre outs and playing with the setting gave me a bit more control vs hooking up to rear outs.

 

Some of them will say "Subwoofer Volume" or "Level", Im just letting you know that it is gain, which is distortion and it will sound better because it's louder since your preamp isnt pushing enough, but that just means that you need a stronger preamp output. Too much gain ruins your coils over time. Say your level is perfect max constant for your subs and you turn your gain up, that is good, but crank the gain and the sup will bottom out and your amp will clip. IMO I would replace the deck or hook the rears to the rear output. Thats how mine are and they sounded great, with plenty of control, but I also have a kenwood with LPF, HPF, Bass Freq, etc etc per set of channels.

 

Good info. I'll have to go back and look, I think my issue was that I could not set the cross over for front and back independently so I was killing the subs low frequency when trying to limit the bass in the doors.

 

That makes sense, most decks dont give you independant control.