Audio for sidekick?

We just bought a 93 Sidekick, and want to put a system in it. What is the best bet for speakers in the stock, or non stock locations. Should we build a box for the back, and not use the stock speaker locations, or use both?
Thanks.

i put mine behind the rear seat in my 93 but i started to customise then in the side pannels just above n behind the stock location but to do that i wa sgoing to us mdf or particle board. however mine worked ine behind the rear seat untill u goo ovv roading with tem unsecure. i secured them and never had a problem since