I'm also with Tony on this one. I realize the you are laying out a bunch of money on the amp and sub, but as you already said, your sound is muddy now.

After installing just a sub, it will be muddy...with good bass.

MB Quart are great speakers, so if you can afford them, it will make quite a difference.

As far as the purpose of the van, just promise you won't get a bumper-sticker like my brother had on his van: "If the van is a rockin' don't come a knockin'"

-Trevor