rear speakers in my truck??

[CASZ71]

For a while now ive been running kicker ds650's up front in my doors off of a audiobahn 2002t and it sounds good but my question is i cant really get to the rear speakers in the back.. If you drive a truck like mine u know.. btw i drive a 98 chevy silverado ext cab.. so i was thinking that maybe i could hook the stock speakers up to my amp also but didnt know if it would be ok.. because right now i have a 4ohm load going to the amp and correct me if im wrong but i think if i put my back speakers on it which are 4ohm and so are my front it would make a 2ohm load?? But the only thing is i dont want to overpower the rear ones and blow them cause the only way ive heard of getting the whole back piece off involves breaking stuff.. So could anybody help me out.. Maybe someone that has a truck like mine.. What did you do???