well the 15 i can argue with i never had a problem with that one it got fairly loud and took the 1500 watts i was giving it very well the 18 is when i started having problems the surround tore from me playing it in the tline it hit my seat for about 15 mins and it started to tear then we took it out and put it in a 4 cube box with 80 inchs of port tuned to around 33 hz and it could barely do a 29.9 on a 3000d im not trying to bash just my experience with the sub the tear was my fault i shouldnt have let the seat touch the woofer and let me say when we put it in the ported box we checked the connections and the ohm loads i set the amp with an oscope and a dmm so something was up with the sub not the install