First of all you have a nice car ! I just bought a New 2009 (last one) and have the following and its very similar to your setup.
I have a Alpine W505 as a head unit, a 400BT bluetooth, I have the same amp (900/5), I have JL 10W6 in a custom (not as nice as yours) box. I also have a set of Focal (polyglass 6.5 set) fronts and Type R coax rear. I am pruchasing a set of 710 Monitors (a dealer here has a overstock set) but I am going to mount them to the poles. I was not sure if they would fit in the headrest. How did the install in the headrest go and I was wondering how do you get around the fact that the 710's dont have buit in IR did you mount a IR somewhere or just using corded headphones. Did you notice how sweet your system sounds, I had the exact same setup in a 2008 Mercury GM and it seems like the edge has really good acustics because it sounds great in this car !!