Here are some tips for ya:
(1) All SVT's have the "premium" sound which includes a factory amp (mounted behind the glovebox). You'll definately want to bypass it if you plan on using the HU to power any of your speakers. Call Crutchfield (888)955-6000 for the amp bypass kit.
(2) Use the factory speaker wiring (unless you get cRaZy and want to put >100w to your door speakers). The system Ford uses to route wiring through the doors makes it very difficult to run new speaker wiring without drilling. A good place to splice into the factory wiring is right after the factory amp using the amp bypass kit.
(3) An 8" sub mounted free-air underneath the bottom of the rear deck powered by a small amp helps fill out the (lacking) bottom end of the system. Check out BMR's
Rear Deck How-To Guide. (4) Soundproofing is a must in these cars both to reduce rattles and block some road noise. I'd do all 4 doors and the trunk with some "high temp mastic" from
www.mcmaster.com. It's virtually the same stuff as dynamat at about 1/5 the cost.
(5) Do a search on "firewall" to read all about routing power wire to your amp in the cabin.
