wow thats alot of stuff to list. My signature contains good stuff. I guess i will create a list.
Wiring-KnuKonceptz.Dont waste your money on anything else.
Subs-If your on a budget I dont know lol. I would go with 10s though. They wont waste much more space and they give you more options. Look at Kenwood, Alpine type E, Rockford Fosgate P2s. If you wanna live a little go with TC Sounds, RE Audio, FI Audio. It all depends on what your looking for. do you like Sound Quality or SPL? SPL=Really LOUD BTW Just massive bass.
Amplifier-I would go with Hifonics, US amps if you want to spend a little. If not then Kenwood is a good start. This all depends on the subs you pick also.
Deck-Any player could be rigged up for MP3 player. As long as it has more than one output set. Alpine 9856 is what i have and Play my PSP through it. Pioneer is also a good name.
Cap- YOU DONT NEED ONE!
2 10 inch subs will fit behind the passenger seat if you build the box right. The amp will go behind your seat. I currently have 2 TC Sounds db-500s in my regular cab. I lost all leg room on the pass side. The subs i recommended will fit great back there. You should only have to go up like one or two clicks.
2003 DSG Mustang GT-Procharger, 3 core IC, some happy gas, full bolt-ons, suspension, wheels/tires, etc. CMS Blower cams, and other stuff waiting for install.
2009 R6-Raven-FE, flushies, double bubble screen, Graves exhaust, BMC, and PC-V
2006 F150-Lariat, 4x4, Daily