If by warranty you mean actually BUYING it from Newegg.. That's just stupid, AMD's warranty is just fine. Any companies for that matter. Umm... As for the CPU... games are more on GPU unless your playing SC2. I think going with the Phenom will be a better bet. But you won't get SUPER fast applications that's for sure. May I ask what video editing software? IF you your using Adobe Premiere, wrong choice for the GPU.
1) If your using Adobe premiere, because of the Mercury engine, Nvidia cards utilize the Cuda and edit the stuff faster than say using an i7 980X w/ a 460 than a 980X w/ 5770. So if you are using premiere look at the 460 768mb vers. There all in the same price range, the 460 has better perf though. And judging by your budget, I don't expect you to SLI this build.
2) Video editing is very CPU intensive, like PS5. Don't expect the Phenoms or the Athlon X4's to be able to edit very fast is all i can say. You can edit better with the Phenoms (since I use Adobe Premiere) but you won't apply effects as fast as you'd like. I mean it's bearable, but kind of slow. So... If you could add a little more to the budget, I suggest going for a 1055T, it has a much faster Video editing ability than the deneb or propus.