One can purchase a Kicker subwoofer at many electronics retail stores such as Best Buy, Future Shop and Visions Electronic. One can also buy them at online shopping sites.
The Kicker CVR subwoofer comes in sizes such as 10", 12" and 15". You can purchase these subwoofers online from the official Kicker website online store.
kicker
Kicker is a much better quality subwoofer than Pyle, and it will have much better bass as well.
kicker L7 or fosgate t1
The Kicker 1500 Watt subwoofer is very, loud, but doesn't have the best clarity and can get muddy. Consider Pioneer subs.
http://www.kicker.com/content/Contact_US
The Kicker enclosed 12 in. subwoofer can always be connected to your factory radio, and it should be very easy to do.
It's a dead subwoofer.
A JBL subwoofer can be purchased from JBL directly. Another option, which may actually be cheaper, is to purchase one off of Amazon or an auction site such as eBay.
Kicker solo is a great all around subwoofer for the price. Good deep bass low price who could beat that?
One might purchase a Kenwood Subwoofer when one goes to stores like Best Buy, Future Shop. One can also shop online on websites like Amazon and eBay for deals.
For the money the L5 is the best sub by far. Then it would be the CVR series.