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Again....it depends what you want your final goals are. I took your original post as 400RWHP would be it. If you want the most you can get than by all means buy a turbo. If you'll be happy with 400-500RWHP I would suggest a blower.
Right now the pricing kind of varies depending on what you get. For a blower you could go kenne bell or whipple. For turbos you could do a hellion setup or go to turbochargedpower.com.