i have two JL Audio W6s hooked up to a Orion 2400D Amp the gain is turned up 1/4 of the way but i used to have two type X's.... i just got the W6's and was wondering about the different models.. i have the 12" W6 V2 D4... i have 2 of them.. whats the difference between this sub and the D1 or V2 models.. which W6 is the best model to have???