The most demanding application you have listed is making movies and even the cheapest of the three systems will do that adequately. By going to the fastest and most expensive processor you will shave some time when rendering the movie but as you are not a games player then I would still go for the cheapest option but personally for video work I would upgrade the RAM to 8Gb and leave the rest the same. If you want to spend more money then change the DVD to Blu-Ray and the processor to a Quad Core. AMD is fine in my opinion.
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