He stated he does not use 3D modeling programs, he is talking only about HD video editing, and I will assume he meant to say encodiing, not rendering. (rendering is what you do in a 3D modeling program)
What the OP is doing does not require a GPU of any significance at all. Any midrange HD card will do the job very nicely, what you really need for this is raw processor power, the more cores the a better, you have that covered nicely with the X6.
Now if you do want to play some games, the 5830 is great card, but is a little pricey for it's performance point in my opinion. I would either step down and go with a 5770, or step directly up to the 5850.(but I think that is out of your price range) If you can find a 5830 for about $200, then I would get it definitely for sure.
Cuda technology? Not a factor here at all.
it was so clear. Thanks. yes it was my mistake. its not rendering. it is encoding and i will buy a 5770..