8" subwoofer? Is it enough?

I have a regular cab Silverado truck I am in the process of designing a system for.  One of my criteria is that it not intrude on the daily use on the truck.  (I can fit my golf clubs behind the seat and would like to continue to be able to do that).  I am considering going with a single 8" subwoofer in a custom enclosure, but have never really thought of 8" subwoofers as being capable enough all by themselves.  I currently have a 10" JL Audio 10W3V2 sitting in my shop that I can make work in my application but I also know it is going to be tight.

I am big into sound Q, but I enjoy all kinds of music, including Rap.

Installation wise, I prefer to stay old school and hide as much of it as I can, that is why I am considering going smaller.  Can you guys give me some input on your experience with current 8" subs?  I have seen the JL Audio 8W7 in some high end applications, but not heard one.  Plus I am not a huge fan of the price, and mounting depth is an issue.

Should I ....

Stick with the 10w3v2 and cram it in there?

Think about going to an 8? If so...reccomendations?

I have an MB Quart Amp 4 Channel amp with a number of different configurations available to get as much power as I want basically.

Thanks

I am pretty limited space wise.  There is a larger depression on the passenger side of the cab floor due to the placement of the gas tank which makes a single sub make more sense because I can place it really low, therefore leaving maximum space above the box for my stuff.  I could either place the 10" in a pretty conventional wedge type box in that depression facing forward, or something like the 8w7 facing sideways toward the corner of the cab to negate the mounting depth.  I am leaning towards keeping the 10 as youve mentioned.  was wondering about experiences with the 8w7 or comparible subs, they looked pretty cool.