Turbowerx has finally posted a dyno curve for the 3.2. Not the 50% bump Marc had initially said, but pretty stout nonetheless. I still think I'd spring the extra 5 grand for the low compression pistons et al and shoot for the 500 hp Box...
http://turbowerx.com/external_pictures/3.2L_Turbo_Kit_Dyno_stk-headers.jpg