There's a lot of reasons not to buy the Dual sub, or anything 'mainstream'.... Small motors, small/weak surrounds, etc.
Alpine, JL,and JBL are about the only 'mainsteam' brands that build good quality equipment, but it will cost you more. You can buy a good quality 'underground' or not-so mainstream sub for about $130-200 that will do MUCH better.
For my smaller setup in my daily driver, I use a Dayton HO 10" (about $138) and a 650-watt PPI Ion 650.1 ($108). It has good output for most small-mid sized cars, but if you want extra bump, I would recommend a 12 or 15" and more power. Two 10's, 12's or 15's would be better, but would put you way over budget. More cone area usually works out to more volume(louder) with less power requirements.