I personally am running 2 Massive Hippo 8's on a Zapco Z2kd and they pound. I have ran and installed 20+ pairs/singles of the Hippos in customers as well as both of my kids cars. They are a performance bargain!!! The price on the Massive web page is inflated and noone sells them for that much. The Newegg price is consistent. There web link originally posted on the Hippo is the new XL sub that is an upgrade to the original Hippo. I have not tried that one yet. I have also used Atomic AP8's, Cadence Sw8's, and DD 608's. All were decent performing subs. The DD's just like the American Bass VFL8's use the same magnet/basket as the Hippo with different soft parts. I keep going back to the Hippos because of the ease to get and price.