Well, the reason why I chose 2 10's is because I am a basshead, and they fit behind BOTH seats well. I wouldn't want a 12" behind the passenger seat and a 10" behind the driver's seat, Haha. Anyway, one 10" or 12" inch would work great for you...even an 8" to be honest (Depending on the company you choose). If you want a one sub setup for SQ and pretty good SQL, you could maybe try this setup...
Sub: One 12" elemental design K series driver...or even better an A series driver
(12" A series 295.00 USD)
(12" K series 135.00 USD)
(10" K series 125.00 USD)
from
http://www.edesignaudio.com
*Also, with either the 12" K or A sub, the box recommendation is 1.0 cuft, while the 10" K sub box recommends .5 cuft.
Amp: JBL 600.1 Mono Amp
(195 shipped in USD)
from
http://www.ikesound.com
Wiring: 4 awg amp kit
(37.00 USD shipped)
from
http://www.knukonceptz.com
Box: Build your own or search online for good sites (I made my own box)
As far as the component speakers for up front go, you were told right in my honest opinion. Rear speakers won't really be needed, especially in a small truck like ours.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif You could try many different kinds of components. Many people like these type of component speakers...Also, I can't remember what size your truck will allow to fit in the door. It will be 5 1/4 or 4". I didn't install my components, so I don't know if my door was shaved to make my speakers fit (friend from shop did the install as a gift

) I got the crystal csc50s components (which are 5 1/4"). These components cost like 209.00 from sounddomain, but they have a deal now where you get like 70 dollars off, so it was like 139.00 for me (in USD).
Good Components:
Crystal
MB Quart
CDT Audio
Alpine
They will probably cost you like 140-300 in USD at most...depends on what you get, I personally recommend crystal though because they sound soooooo clear and they have excellent midbass. Although CDT's are nice too...
Lastly, you will need an amp to power the components because the sub amp (the JBL) is a class D amp, and is made specifically for subs because it is power efficient. You will need to have for example a class A amp for the components. I have a pioneer GM-X364 which is 70x2@4ohm. I got this because it was really cheap at the time from a friend. Anyway, the JBL P80.2 amp is a great match for the crystal components for 89.00 if you decide to go with them.
As far as car audio goes, I'd stay away from Sony. I would invest in a Pioneer headunit...such as the Pioneer DEH-P7400MP for 229.00 USD from ikesound.
Total cost in USD ends up being at most (if you get a K series driver)
135.00 12" K
195.00 JBL 600.1
140.00 crystal comps
89.00 JBL 80.2 amp
229.00 Pioneer HU
50.00 Box (if you buy online)
37.00 Wiring ( you may need to spend more for the component wiring)
-------------------------------------
1104.00 USD (At most add 150.00-200.00 for shipping, taxes, more wiring, etc)
If you have any more questions PM me and I'll be glad to help you out some more.