I installed a set of Pioneer TS-D1720C's in my Jeep last year, they are 6 3/4", although they wouldn't mount to the factory mounting points. Had to use a Scoshe SAC656 adapter plate, apparently Chrysler used 7" openings, as with these adapters everything bolted right in.
Mounting depth on the speakers was 2.5", so 2.15 should be fine.
What amp are you using, the stock Infinity amps that are mounted to the speakers? Those are 2.7 ohm amps, I believe. I'm kind of loathe to put anyone through the pain in the ass of running new speaker wire, but once it's done it's totally worth it. I put an amp under the driver's side rear seat, fits nicely and there is a ground point right there under the carpet already.