What's your inflow/outflow temps? I have a silverstone as you suggested and another fan I had sitting around going now. Removed those noisy stock fans. Outflow temps dropped 2-3C with dual fan over stock so I am hoping all is good.
EDIT: My outflow temp is about 45C; gets up to 60C on the metal casing that exposed to the outside. God only knows the chip/inside temp.