Maybe I am just being cheap, but why not keep the the Kickers? I have always been a fan of Kickers they are very good subs and can last years. The Solo Baric models have always been my fav.
My two cents: The thing about placing subs in the 4runner is you don't really need competition type subs for clean bass, since the subs are in the cabin it does not take much for clean sound. I have a single 10" and I love it, very deep and clean bass, But I am pushing it with a Fosgate 200 bridged, and the ten is a dual coil.