Well for me I don't like free air subs becasue I feel that the bass is too sloppy...IMO I would sell them and get two nice 12" subs and put them in a sealed encloser facing up or to the tailgate/back door.. If you must go with these subs don't cry just please please please get rid of that lagacy amp! I would like to know how your planning on running 4 speakers with that RF 100.2.... Don't get me wrong I love Rockford amps but that particular one is to me just to small for four speakers unless you have cheap ones....I would sell both the amps and try to get just one nice 4 channel amp for the highs and mids and well you'll just have to spring for a whole new amp for the subs..
If this isn't enough info one what your options are then just give me some more detail and well work on it...like how much you wanna spend, what brand subs you'd be willing to get or how much you could spend on a new amp for the speakers you already have...also what kind of highs and mids do you have? you see more info on your setup is needed to give you better ideas...later