upgrading CPU

my main use for my computer is video editing and then a decent amount of photo processing. my specs:

mobo: EVGA 750i
HDD: samsung spinpoint 500GB & WD Caviar Black 1TB
CPU: Intel E8400 3.0GHz
video: EVGA 9800GT 512MB
ram: 4GB Corsair XMS2
os: win7 64bit ultimate

i am kinda sure that an upgrade on my CPU would get me the most performance since thats the oldest part next to my graphics card which isnt used nearly as much i dont think. my mother board is kinda old so im sure im limited to what i am able to get but i would like to know if upgrading to Core 2 Quad would be a significant increase in performance.

thanks.

i have similar set up, i got E8500 cpu with evga 8800GT
you get can Q9950 cpu for $275

I am waiting to get Core i5-750, but i will need new mobo and ddr3.

I dunno if i'd bother, but it depends what software you use. Your batch conversion speeds will probably increase a bit, but since the cores on the quad core may be slower other things might slow down very slightly.

i edit video in Premier CS5 and use LR3 to process a lot of photos with some work in PS as well

Ok then the upgrade might be worthwhile. Just work out what the fastest Core2Quad CPU is that will work on your motherboard and give it a go. It might be worth looking on ebay.