Stereo & Electronics - newbie questions about sub?

ok im wanting some more bass
1 is it possible to hook up a sub and amp to the factory head unit?
2 if so i was wanting to go with a 10" P2 in a stealth box and use a supporting amp probably a rockford fosgate amp.

I dont want to have the best system on the block or nothing just a little more bass, and i can get everything pretty cheap because a buddy of mine works at best buy right now and said he would help me out

yea you can use an aftermarket amp and sub... you are looking for a LOC or "Line Output Converter" and you will patch in to the speakers in the way back (either left or right side)