These are the stuff I got right now
2 rockford fosgate amplifiers (one 2-channel and one 4-channel)
alpine head unit + CD changer
a good quality 12" subwoofer (can't remember what brand it is, but is a good one)


What is the best way to hood them up. I only have very few knowledge about car audio. So please people who are willing to help give me some tips.
Can I keep the factory speakers?? How bad would it cause if I don't change those speakers. What other things I need in order to make a fine audio system??

Would it be better if I use my 4 channel amp to run the speakers and keep my bose HU(6 dishes in dash). Or should I change the alpine HU?? If I changed the HU, should I use my 4 channel amp to run the speakers or use the HU to run the speakers??

Also, I got a 12" subwoofer. May buy two 10" subwoofer just because they may look nicer. Would my 2 channel sub too much for two subwoofers??

 

you dont have model numbers for the amps or subs.. so Im not really sure if its too powerful, too weak, or good enough to push your 12's... anyway if you can afford it.. I would get new speakers all around... w/ your equipment here is what I would do.. put in the Alpine head unit in the front, I'm assuming your alpine is like mine.. and has 3 sets of RCA pre-outs (front, rear, sub).. wire it up and hook up RCA cables (you can run these either down the center.. or down the driver side.. and run the power cables for the amps down the passenger side) and run them to the back seats/hatch area... If i were you I would also replace the door speakers.. now run your power and remote wires down to the back of your trunk/hatch area.. to your amps.. hook up the head units RCA output for the front and rear to your 4 ch amp... hook up the power, ground, remote wire to the amp.. hook up the amps output to your door speakers.... now do the same.. all the wiring (RCA for sub, power, ground, remote) to the 2 ch sub amp.. (im assuming its bridgeable)... connect the output to your sub bridge it.. and you should be coo... now run your AI-net cable (you said you have alpine..so im assuming its AI-net head unit/changer like mine).. anyway run the changer cable to the back.. and mount your changer then plug it in... make sure you separate the power wires.. from the speaker and RCA cables as much as possible to eliminate the chance of picking up interference (alternator whine)... after you've done all this wiring/hook up.. your system should work.. w/ the head unit turning on.. the 4 ch amp powering the mids and tweets (door speakers) and the 2 ch powering the sub (subwoofer).. maker sure all the power rating, and ohmage (look in the manuals for the amps and speakers) are all correct... you'll need to buy RCA cables and amp/power kits... get them at your car audio shop.. I use Phoenix gold wiring.. i got 4 guage wiring... but what guage you need depends on how much power your pushing..