It comes down more to you wallet. The best thing to do is make sure the amp is equivilent on power as what the sub can take, you can actually go a little more on the amp over the sub if you need to (just don't crank the amp).
So if you have a sub that runs 300 watts rms at 4 ohms, make sure the amp puts out at least 300 watts rms at 4 ohms. You could go to an audio shop see what they recommend and price it out on the internet. Also, I believe you will want to point the subs downward if you can in a Jeep. My friend had a nice enclosure that went behind the back seat of a TJ. Of course there was no more room for storage after that behind the back seat.
