I just installed a Phoenix Gold 10-inch Titanium series and am very happy with the results... although their manual recommends using 2 layers of 3/4" MDF due to the "intense internal combustion chamber." Now correct me if I'm wrong, but internal combustion is what my engine does, not my subwoofer.. right?

 

Alpine, Audiobahn or Kicker. Fosgate sucks, the only thing they have that are decent are amps, everything else they get blown out of the water. Also, it doesnt just depend on the brand of sub that you want, it depends what you are wanting to do with it. If you want SPL (Sound Pressure Level) then you would want to go with Kicker or Audiobahn. If you want SQ (Sound Quality) then go with Audiobahn or Alpine. Audiobahn makes some MEAN amps, too. (www.audiobahninc.com) www.ebay.com can get you some greatdeals if you know what you're looking for. I sell 'systems' in my local area as a way to make some quick cash and I always use ebay and I make around $250 off of a complete system (Subs, Amp, wire, sometimes a head unit) and my prices are still below retail, that just shows you how much you can save on ebay.

Edit: About the brand: Everyone has their own personal opinions and likes. I stated the 3 brands that I think are the best, as well as what other people have already done... stated what they like the best. No brand is "the best" brand on the market. Every brand has something saying how their brand is better than everyone elses brand, but none of that is true. It's basically politcs for audio