I third Sound Deadener Showdown. Knowledge and customer service is top notch. He may not get to the initial email that day but once he does start your order you'll be happy all the way through. There is other stuff that gets the job done for cheaper but, never quite as good or with the same ease of installation. Don at SDS actully recommended another comparable product for me when I had budget constraints. I used it. It worked. It was nothing like using his stuff. I'll never use something else again for my personal installs.
What about the NVX stuff? It looks like Sonic has a deal for 20 sq ft for $60 and it comes with 20 sq ft more for free. 40 sq ft for $60 shipped? I'm not looking for perfect, just something decent for a daily driver.