I replaced the door speakers and though it sounds better I do not have nearly as much volume. I can turn the radio all the way up to 30 and I'm still looking for more and no I am not deaf. I plan on using the pac audio interface device and a 4-channel amplifier or should I go with a five channel with the 5th channel for the future subwoofer upgrade? Looking for brand suggestions probably from Crutchfield

 

I didn't have a subwoofer in my XLT. The route I took was to use a 100W amp for the four speakers (sits in the upper glovebox, where I drilled some vent holes in the top) along with the head unit inline harness, and that provided great sound to the replacement 6x9's in the front doors. Rear speakers really don't do much, frankly, but the fronts do the heavy lifting.

For the subwoofer, I just went with a powered sub and had to run a remote-on wire from the front glove box to activate it. The real challenge was tapping into one of the rear speaker wires to send signal to the sub. Fortunately those wires were available in the wire loom exposed by the B-pillar between the front and rear seats. Plus, running the power leads from the battery to the rear seat was fun, but doable.

I originally went with the larger Rockville subwoofer, but I had to leave the rear seat removed as it was too thick to allow the seat to be installed:
I've since decided to replace it with their thinner model so that I can reinstall the rear seat (just haven't got around to doing it yet):
Here is the audio processor that I used in order to feed the subwoofer. Since the signal is so weak from the rear speaker you'll need to improve the gain to the sub in order to drive it:
Good luck, and there are many threads here in the forum for audio upgrades. Before you begin your quest I would highly recommend perusing those threads, they certainly helped me out immensely.

 

I have an audio control lc-5.1300 that works well

jl subs

 

Yeah, my LC-1i is like the little brother, but it does have everything I need (including the most important part, the gain control).