Very nice equipment list!

As for your sub configuration, there are always pros and cons depending on what importance the system plays in your Crossfire. If you're out to install a system so it doesn't take any more room in your car, then I would say use the rear speaker location for subs and it would definitely sound good.

On the other hand, if you're going for concert or studio quality sound reproduction, I would lean towards building a sub enclosure within the hatch area. It would be a huge improvement for the sonic and tactile enjoyment over subs in the factory location.