question re: 6600 vs 9450

Hi All, it's been a while since I messed around with hardware so I'm not as up to date on it as I used to be. But I've been thinking of building a new computer, and to those that are familiar with the inner workings of the C2Q 6600 and 9450, do you think the extra cost of the 9450 justifies what performance increase it brings? I plan on mostly using this new computer to 5 box wow, but will also be playing some new games such as fallout 3. I do a fair amount of video converting and am thinking of getting into 3d modeling. Are there programs out there in these categories that take advantage of SSE4 or will be doing so in the near future? or is SSE4 just a marketing checkoff point for now?

I've seen enough hardware that has superior spec on paper that underwhelmed in practice before, and am just wondering from those that have used these 2 processors if they noticed any noticeable performance differences or if you think it's even worth it? Differences in the faster memory and 12mb cache? I'm not a huge overclocker as stability is more important to me than speed, and I am no longer a PC hobbyist so I dont feel like messing with aftermarket cooling solutions and such.

The consensus from my own research seems to be that Q6600 is the better bang for the buck for now, but I would like to future proof this box for at least 2 or 3 years ideally. Your opinion, Q6600 viable for that duration? or will I need to upgrade again in like a year if I go with it?

opinions and feedbacks welcomed, and thank you in advance for your help. Have a good day! :)