Adding subs/etc to my truck...

...Need input from some people who know their shit.

Here's the deal. Looking at picking up a radio that draws about 14amps on high power, so I can't run it off cig lighter. Have to run a dedicated circuit into the back (Has remote-head capability, face can be mounted on dash and run the cable back to the radio) for it. Since I'll have electricity back there, i've been wanting to add a little more bass to the stereo. I have a 300w amp, looking at picking up some shallow-mount speakers (Pioneer has decent prices, and their stuff isn't too bad).

Mainly want this stuff to be discrete and retain use of the back seat (and foot/leg room) in my truck.

Questions:
1) Running the big 4awg cable from battery to back along the drivers side. How do you get this through the firewall? I can't really find any openings in it for this sort of thing... am I not looking hard enough, or am I going to have to drill it out? Right now i'm considering having a car audio place do this part.

1.5) Probably run the remote turn-on from HU to the back there along the drivers side as well. I assume this is fairly standard. Audio from HU and the remote-head for radio will be along the psgr. side. Ferrite beads will be placed on almost everything to prevent the radio from interfering with everything else and vice versa. Does this sound like a good plan?

2) Mounting everything. Amp has slots on the side for bolts, but how do you attach the bolts to the floor of the truck? There's currently two brackets on the sides holding the plastic bin-divider-thingy in (which will be coming out), can I make an ABS floor and mount everything to that or will it rattle? What about vibration.... Radio's mil-spec, so i'm not too worried about it, but what about everything else? I may do an ABS base to mount the amp/dist blocks to and mount that base to the truck.

3) Porting subs... probably do a custom-built enclosure for the subs under the back seat... mainly want the amp/radio/subs somewhat discrete. I've seen the pre-built enclosures for under-seat install, might use that as a template for what i'll be doing. What's the best way to get good sound but still keep everything discrete?

Pictures will probably come later this weekend.

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