Cheap is a very relative term so its hard to say what you consider cheap. Supercharger will be cheaper then a twin turbo for sure. 500+ hp without modifying at least some of the 370's engine is just asking for it.
These cars are missing low end torque in my opinion so a Supercharger just seems like a natural choice to me. Having said that if you want more then 450 on these cars I would say Twin Turbo is the way to go.
If I ever go the forced induction route I will probably go Supercharger.