Can anybody give some suggestions of other lower price alternative to the JL audio 13w7 both in output and sq? I obviously know that you often have to pay for quality. But are there any other subwoofer that have about 90% of what the JL w7 line offers at about a $500 budget. For same level of output, I am also willing to go with 2 subs. I am currently using a Audio Frog Gb10 d4 ported and pushing it with the alpine PDX V9 5th channel. I like the sub but feel it is lacking a little bit of output and was wondering if there was something else out there.