Researching New Sound System

Hey Tacomans!

I am looking in to upgrading my stock sound system and wanted to get some suggestions/opinions before I go blowing what little money I have on these big ticket items!

I have done quite a bit of research and I started out with little to no knowledge of car audio, but after reading stuff on here (especially posts from Mr Marv) and things on other sites, I have decided on what I feel is a solid (budget) system.

I can't purchase everything at the moment, but I would like to at least install something before I leave on my big move up to Alaska. I will be driving about 5,000 miles and I want some nice tunes during those lonely hours!

With that all in mind here is my wishlist:

Front doors: 6.5" Focal 165 A1 - $150.00
Rear doors: 6.5" Focal 165 CA1 - $90.00
Subwoofers(2): 8" JBL GTO804 -$50.00each
Amplifier:

MRX-V60 - Alpine 5-Channel Subwoofer Amplifier

Alpine MRX-V60 5-Channel -$220.00
Head unit: Pioneer AVH-P2400BT -$300.00

If I was to do the cheapest upgrade possible for my trip, what should it be?

Another option I have for the amp is buying a cheaper 4 channel amp and using a Boss MR800 that my dad has laying around for the subs.

Would those subs fit behind the seats in a box? I am honestly planning on fiberglassing under my rear seats and installing the subs down there. Seems like a fun project.

Any money saving tips are appreciated! I spent all my money on the truck and the military doesn't pay me enough!

Thanks for your input!

-Ducky