I really wouldn't bother running the rear speakers off the JL amp - your chosen amp will give you the ability to run the fronts active, or I would swap the 450/4 for a 300/2 and give the ZR's the right power to control them as much as the W7. Just IMO of course.
The amps also have built in crossovers which can be used, so that might be what he was referring to. But you will need an EQ to set it up when it is installed.
If you mean the Phantom face headunit (Alpine CDA-7998R?) then a) that will sound awesome if you used it, and secondly if it is for sale, drop me a PM!