Do you have any decent craigslist markets in your area?
I used to be skeptical, but for what i've gotten recently, used car audio deals can be AWESOME.
I'm currently running a JL 12w6 in my burb, after buying it for a temporary boat sub for $300, including box.
Just bought a 10w7 for the boat, in a nice box, with a mediocre amp for $400. That is a 7-800 sub, alone.
I've never done any competition stuff, but i've always liked JL. Thinking you are going to be looking for something better, but i've got a 12w3 in a box, with amp that i could sell you cheap.....