Your head unit choice is good, I would stick with that.
I would go with some high quality components up front like :
focal utopias ( I have them and love em)
dynaudios
cdt audio
if you dont want to spend too much money
ID chameleons are good.
as for rear fill, its up to you how much you wanna spend back there. I would go as cheap as possible, **** the backseat passengers
I would go with a nice 4 channel amp. I just happen to be selling my Brax x2400 //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
but I dont know if you want to spend that much.
You could always go with their lower line, helix. Excellent amplifiers.
could go
PPI
Xtant
soundstream
those are all in your price range.
for subs, what do you want to do? how many? how loud? ported/sealed?