Subs
You could do something like these that custom fits under the back seat.
http://supercrewsound.com/commerce/p...Id=62&catId=62
http://www.amazon.com/dp/B0013N0U9O/...SIN=B0013N0U9O
http://supercrewsound.com/commerce/p...Id=62&catId=62
http://www.amazon.com/dp/B0013N0U9O/...SIN=B0013N0U9O
Just go with MTX Terminator single 12 package. You can get it for 169. They also have dual 12s in a box.. Or look on ebay for subwoofer packages for you truck. I found one for around 380, but I went with the MTX. It may not fit under your back bench but hits pretty good for the money. Good price too.
My Sub is mounted under the front Bench seat it the center. It's awesome, not very comfortable if your sitting there though...
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Depending on if you have people riding in the back. I got this Downfire box off ebay for $100 shipped. They also make front fire (or forward forgot what it's called) For 1 10s or 12s. I got 2 kicker C-10's in mine. Got them from crutchfield buy on get one free for $100.



