We shoehorned (and sawwed) a set of MB Quart 6"x9" coax in F150 door, and they rocked, A LOT of midbass. You can find them in your budget on e bay....but be prepared to trim, bend, wrestle and curse a little. It'd be easier to do 6" coax in a baffle, and call it a day.
I may still have a set of MB Q Reference series 6x9s, I'll look and see.