Ok, I have the JL 12W7.
I've heard IDMAX, Rockford Fosgate, JL Audio, Kicker, and a couple others I can't recall offhand.
I paid $750 for the 12W7, and I think it's worth $500, if you can get it for that. The SQ is definately better than what I've heard elsewhere (though I grant you I haven't heard a Brahma, ED or XXX). It is quite powerful and does need a fair bit of power if you want to hit high SPL numbers, though for pure SQ, not a lot of power is needed. It could probably take 2000W all day long without breaking a sweat, because it's heavily over-engineered, and just plain tough. If you have the money, I'd say go for it.
Oh, and slightly off-topic - I think everybody who states an opinion on a subwoofer should list those that they've actually heard in-car before they start saying what is better. This will help eliminate posts that list subs that are "better" or "equal" when the person making those claims hasn't even heard them. I'm not saying this in response to any specific post(s), just a trend I've noticed lately.