I had the same question about 2 weeks ago so I did some research and I found out if you really want to see some good horsepower gains you are going to have to spend at least 4500 dollars. But by far the best supercharger I found was the x charger extreme supercharger and it costs about 5500 without install. But it gives you about 140 hp gain. That's what I am going for now. Hoping to get it by January.