You can get the MTX lineup from http://www.woofersetc.com Where in TX are you? As long as you're not in some small country town there should be an audio shop in your area that sells the JL boxes. There's not a big advantage to buying boxes online. It usually comes out to about the same or even more than in store because of shipping when buying online. As far as amps and speakers, i'm all about getting those online. Just with boxes, there doesn't seem to be much of a difference.
Also, the MTX box is pretty much the same as the regular JL box. I think the only difference is that the JL comes carpeted, and MTX is color matched paint or vinyl. JL does offer a different style box called the Vantage box. Personally, I like the vantage best, but any will do.
hey dude in austin what kind of system you got?? i am looking to try and find someone who is louder than me but haven't found anyone yet. what you got in your car man?