Not sure what you can get used, but if you'd prefer new these might be worth a look (not sure if you were looking for ported or sealed):
http://www.svsound.com/subwoofers/sealed-box/sb-1000
http://www.svsound.com/subwoofers/ported-box/pb-1000
Personally I'd spend an extra 99 bucks for this if possible (more power, better driver, etc.):
http://www.svsound.com/outlet-specials/view-all-outlet?page=shop.product_details&flypage=flypage.tpl&product_id=200&category_id=5
Agree with Roscoe on the power (at least for subs from reputable manufacturers) and integration points, especially since this is mainly for music. Best of luck.
http://www.svsound.com/subwoofers/sealed-box/sb-1000
http://www.svsound.com/subwoofers/ported-box/pb-1000
Personally I'd spend an extra 99 bucks for this if possible (more power, better driver, etc.):
http://www.svsound.com/outlet-specials/view-all-outlet?page=shop.product_details&flypage=flypage.tpl&product_id=200&category_id=5
Agree with Roscoe on the power (at least for subs from reputable manufacturers) and integration points, especially since this is mainly for music. Best of luck.