Well like you said, the Xcon is great. If you care about sound quality and loudness, the Xcon is the perfect sub for you. I currently own a 12" and love it. Beats my old JL Audio W7 in every way, and that W7 costs $200 more. So it's not all about price. Another thing to add, the SSA is the company that makes the Xcon. Their customer service is great and I've never seen 1 complaint about that company. All of their products are made according to order, and they're built here in America.
You see DC subs filling up 1/4th of the subwoofer classifieds section. Go take a look there. If they were such great subs, wouldn't most people be holding onto them instead of selling them? And the customer service isn't the best, reps are pretty nasty. I've never seen a company so uptight about having their product prices made public.
Give us some more detail of exactly what you're looking for. Do you want a sub that gets loud and sounds good, or do you not care about sound quality at all and just want something that pounds. Type or car you have. Do you have an amp already? If not, how much can you afford to spend on an amp? Just some details that can help us give you more accurate opinions. Thanks.