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"Massive" woofers is a two edged sword. REAL high output woofers have large motors and surrounds to compensate for having incredible amounts of power thrown at them. Companies like Audiobahn, Audiopipe, and Volfenhag have caught on and made cheap woofers with huge magnets, large surrounds, and very thick baskets. All the extra weight and bulk gives the impression of a real high output woofer, but they perform even worse than small woofers most of the time.
The only things that allow you to tell the difference between a good subwoofer and a bad subwoofer are experience and common sense.
I recommend using the search button. Read about competitions, and what subwoofers and installs are used there.
EDIT: Just to mention, if you're just starting a system, don't worry about getting competition grade equipment. Get something that works for you. Get something that sounds genuinely good to you. Don't worry about what anyone else says- they won't be driving your vehicle every day.