The QX9650 is a $1000 processor and while it is the fastest, the Q6700 2.66GHz is only $540. That's half the price for only 0.34Ghz less speed. I doubt highly that you will feel the difference and clearly you are not getting twice the power yet you are definitely paying twice the price. Personally I would go for the Q6700 and use some of the money saved to get 4GB of memory. While Windows XP will only use 3.25, it is still better than 2GB and Vista 64 will use all 4GB.
I would strongly recommend that you get a new power supply as well (although I think you said in another thread that it failed). More CPU power means more power consumption. Especially for us videographers who tend to have a lot of hard drives sucking up power.
Sure, HF, I have been told though to try and keep things INTEL throughout? INTEL MoBo and INTEL CPUs?
I haven't seen an advantage to doing that since the the first two years of the Pentium. Obviously you can't mix AMD & Intel chipssets/cpu's but I have an Intel with a Via chipset that's been working, no issues, for ~6/7 years now (it's worked better then any other intel product I've had after that). I've experienced intel chipsets sometimes lack features other have that are pretty useful too, but if you don't need those features then it doesn't matter (intel is normally pretty good because they do a little bit very very very well, not sure if that's the case with the core 2 line)
But with the AMD chips already out, if people don't have issues, they're same price and/or cheaper & same speed/faster, I see no reason to not go with them if they're at an advantage. Even though I love the AMD XP/64 line I was planning on getting an Intel Core 2 if I had the $$ because of how well they are.