You can use this comparison site to compare your two processors. In the right hand box just scroll down and input the processors of your choice and in the left box choose whether to compare their performance for games, sysmark, office etc. Video editing depends on a good CPU, then the ram, the possibly graphics card lastly if you are making graphics and 3d rendering all the time. You don't say how much RAM you have but increase it to 6Gb or 8Gb if you can (but you will need a 64bit OS if you want it to be recognised).
Gaming stresses graphics so if that is what you do more than video editing then you might want to upgrade your video card (the HD5770 is considered a better performer at the same price as the GTS450)
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