The reasons I think that there will be so much additional power in the SRT is that the manifolds are the between both models are the same despite the SRT6 having twice the HP (ok, maybe not quite twice but you get the point). Plus looking at the numbers the C32's are getting with Evo headers.

Of course there is only one way to be sure how much power is produced. Get the things built, installed, and a car on the dyno.

I for one am very ready to purchase the headers.