I just bought a 10 inch sub and a box for my daily driven explorer, i have an alpine cd9801 deck. now to run my sub do i need an amp....after reading my decks owners manual i get the impression that i dont. and if I do what would be a good amp to run....  

How may watts would your head unit be feeding the sub?
I would say you would want a channel with no less than 40 watts feeding the sub by itself.

p.s. You may want to watch out.  "Explorer", "sub and box", "Alpine".  Those are dangerous words round these parts. You didn't hear it from me though.  

look to the specs on the sub K, it will say on the box or specs somewhere the continous and max power figures,run with the continous power figure. hope ya got a simple sub,and box set,aka.a single voice coil set up,maning you gor one set of terminals to hook up,your head uniit may drive the sub,but your shortchanging yourself if you do on sound,look on the back of the head,,there may be some RCA phono jacks. then..you open up the possibilitys for better sound! giv a holler for mor info! and dont be intimidated,it gets easyer as you go!