I would say no, at least not for $140. I have the Q6600 and it's blazing fast even at stock speeds.
I believe the Q9450 OC's a bit better than the Q6600, but every chip is different, so you'll have to try for yourself.
Actaully, the Q6600 OC's better.
The Q9450/9550 hits early FSB walls. Topping out around 3.5Ghz