The Q9550's 8.5 multiplier may allow you to go a little be further but the sweet spot with Penryn seems to be between 3.4 and 3.6.
What is your motherboard and the cooler you intend to use?
IMO, the Q9550's does not worth it since it costs $200 more than the Q9450.
hi thanks for the reply.. ok my mobo is Asus Rampage Formula Intel X48 and will be running a very good h2o setup, so basicly ur saying if i want to get past 3.6ghz i will have to spend lots more on the QX9650 which would not at all be worth it
also does the q9550 or q9450 have unlocked multi's