With that kind of budget and subs taken care of.
I would say get yourself some sound deadening (dynamat, roadkill ect) and properly cover up your doors. Make some solid mounts for your aftermarket speakers and run fresh wire with a sound deadening mat to catch some of the backwave.
Then have your headunit (nothing wrong with pioneer I would even suggest it before finding out you have some of the add on components but $1.5k are you prioritising right?) I am guessing you didnt get any premo intergrated headunit and from what I saw from a quick search it appears subaru isn't going that way gets its a rather simple double din headunit swap. A little surprising but not in a bad way in.this day and age.
I have no idea what prices hertz or focal splits go for in the states without links to sites so cant recommend anything specific and without anything specific cant match an amp/amps.
I second what waco has said about rewiring the battery and alternator it is definitely worth the effort and money.
So sites please because crutchfield and sonicelectronix cant show me much of anything for an sq build I would be happy with in my own car.
Edit: forgot to mention no real point to a sound processor with a high end headunit that is already setting you back in excess of 1 grand. I seriously doubt your ears will be able to tell the difference although granted a processor like the bitone has lots of extra options for tuning and presets. It is really best used when intergarating an aftermarket system with an oem intergrated headunit/multimedia system.
Edited by Stonerboy779, 10 April 2012 - 05:10 AM.