okay i was talking to my friend because he wants to install some subs in his 2003 honda accord. well if any of you guys been in the 7th gen accords the stock cd players are really integrated into the dash

well there is a dash kit for the car....but it is below the deck down by the shifter....so basically if he were to get a aftermarket deck the stock deck would still be there... so might as well use the stock deck because its a decent deck...
we never checked the back yet but im pretty sure it doesnt have the RCA outs... how would i get a signal to the amp using a stock deck? someone told me line out converters ?
how exactly do they work? and will it work for a amp?
any help is appreciated guys !