Although this isn't a Q6600 v. Q9xxx thread please allow me to comment on this point.
I've been reading many of the Q6600 v. Q9xxx threads and I've come to a personal conclusion. That is "to each his own." May I elaborate just a little?
The Q6600 will, I think, go down in history as one of the best cost per cycle of quad cores (or whatever measurement). It is a real killer, a great OC-er for a quad, an all round great processor and, except for the extreme processors, none of the q9450 or q9550 or q9300 are gonna beat it for jobs like OC-folding, or even for gaming although many of the dual cores are considered even better for gaming. (I disagree. Most games are more limited by the GPU, not the CPU, but I digress.)
But the q9[45]50 will both have their place in the pre-nehalem historical record.
Some people, (such as myself), have different priorities. Mine include quiet, low heat, low power, and then quad speed. The q9450 (still on backorder at BLT) will be the piece de resistance of my compters. It will literally be by my bedside 24x7. (I'm disabled so I'm not able to get out of bed easily. This new tower build will replace my ailing 5 year old notebook P4. New flat panel, wireless keyboard and mouse, and I'll be all set..once I get the q9450 shipped!)
If I already owned a q6600 I would spring for an upgrade to a q9300, q9450, or q9550. That's just IMO.
For a new build and with my set of priorities, then the q9450 (or 9550) will be the right and best thing. For me. IMO. To each his own.
Please overlook any lack of netiquette on my part. I'm still relatively new to these forums and trying to keep up with everything I've got (whatever brain cells that are left).
Thanks,
Edro