You sound like a cool guy Dave, can I call you Dave? Here's a run-down of what you need to know; I'm going to save you, and several other people a lot of time trying to explain stuff to you.
First of all, don't ever pay full price for JL Audio equipment. It is solid product, but way overpriced.
Secondly, do not consider brands like Kicker, Boss, Sony, Rockford Fosgate (for their subs anyways). All of these companies have NOTHING special to offer and will be a waste of your time and money.
Third, you will never need a capacitor for your system, ever. No matter what the guy at the audio shop says. There have been a few thorough analyses of the usefulness of capacitors, and they will no help your system in any capacity(puns all day, son) whatsoever.
Fourth, don't listen to the guys that try to tell you that you need this, that and the other. Especially the ones that tell you to drop 500 dollars for a 1500w amp. You seem like you're trying to have a reasonable amount of lower end fill, and therefore there's no logical reason to run an amp that expensive. They are only telling you this because they think that if they recommend expensive equipment that, by default, they are experts. Get the best bang for you buck you can, without jewing yourself out of a good system.
I don't know what your exact budget is, but for about $500-$600 dollars you can have a respectable sub-stage