alright so i have never messed around with a audio system before and i am looking to put a enclosure under my rear seats in my 2007 f150 supercrew.
i have found these custom boxes on different websites.

http://www.supercrewsound.com/shop/detail/11/33.htm

http://www.subthump.com/images/ford/F150/150f-t.jpg

http://www.supercrewsound.com/shop/detail/11/34.htm

http://www.topedgeonline.com/detail.aspx?ID=13986

which one would work best?
what kind of subs would fit in these?
what would be the best type of subs to fit in these?
and what size subs would fit in these?
and what am i looking for with a amp?
what is mono and stereo?
do i need to have a head unit or can i just use the oem radio that came stock in the truck?

i know this is a lot of questions but i really just need some help with installing my first system
i would really appreciate it if you could help me out
thank you