I'm looking into a dedicated amp for my subs so now I'm thinging what should I do with the rear channels I have spare on my Profile AP1040...

The front is JL VR 6.5 coax, I'm thinking I don't need highs from the rear doors, just midbass I think.

What range would a mid bass driver usualy run? 80 - 2.5KHz ?

I'm on a budget too, so what would be a basic way to do this?
I have the HP filter for the front channels at about 100 - 120Hz as this seems best to stop the crappy ford pannes vibrating.
In the midbass rear, I think I'd want to go from a little lower, so a passive crossover?