I second the Lanzar Opti Have personally heard them and wanged on them and they will take power and play flat in super low enclosuresLANZAR OPTI1535D 15" 3200W Car Optidrive Subwoofer Sub (068888879033) | eBaylanzar optis get loud and are really nice subs for the price
NEW AMERICAN BASS XFL1544 15" 2000W CAR AUDIO SUBWOOFER SUB 2000 WATT | eBay
also american abss xfl subs get really loud also