The GT1 cam is going to make you lose more low end then you would if you installed headers. If you don't care about going with boost (although I recommend getting boosted), then you should get a good set of rockers instead.
I went the NA route and I had the GT1 cam installed for a little over 2 years with a stock d/p with no problems. When I finally got my TOG headers installed it took my from a 14.7 to a 14.4 1/4 mile.
Headers are great for a cam or a rocker build, but I don't recommend going the NA way. It was a lot of money for very little gains.