Best Company To Buy A Nitrous Kit From

Going to add a nitrous kit to my car. Only looking at jetting to 150 hp to help if I get a god awful light (and I do), and maybe step it up some for a street race, even though I'm too old for that. Who is the the best source from a customer service standpoint. I'll need someone to walk me through from selecting what I need, to installation. I've been looking at Nitrous Express and Nitrous Outlet. Thanks!