As far as I can tell... NewEgg's combo deal with the P5Q Pro + 4850 has ended.
But the combo deal with E8400 + P5Q Pro still exists... it's a $35 discount to buy both at once. $304.98 total.
P5Q Pro (alone) - $149.99
Q9450 (alone) - $329.99
TOTAL COST - $479.98
By going the E8400 + P5Q Pro route... you'll get similar or better game performance for $175 cheaper. (read: more $ to spend on a better video card!!)
Here's another way to look at it...
Q9450 + P5Q Pro + 4850 (~$200) = ~$679.98
E8400 + P5Q Pro + 4870 (~$300) = ~$604.98
Unless you think you'll keep this CPU for 3+ years... you'd be better served going that route, then buying a Quad-core for around $150 in a year or so when Nehalem hits and Quads are a bit better utilized. Then you can afford to upgrade a step to 4870, and STILL save over $70. That'll give you a cheaper (and far superior) gaming computer.
That's what I'd do, anyway.
Moo.