Impreza WRX upgrade

Im looking at getting a WRX one of the things that I think would be cool to get is the $5k Cobb Tuning RT Spec High Output System (Stage 2). but is the Street legal in the states and is it worth the money?

the people here are not the ones to ask. ask at http://www.i-club.com/forums . i looked at it, and you suyould find out if the price is with installation, but your best bet is to ask at i-club, they know their stuff.

Thanks