Which GPU do I really need?

Urlier, some nice guys confermed that the XFX 7870 Double D is a nice card.

http://www.amazon.com/XFX-FX787ACDBC-1050MHz-2XminiDP-Graphics/dp/B007MUKAMO/ref=sr_1_3?s=electronics&ie=UTF8&qid=1364013544&sr=1-3&keywords=xfx+amd+radeon+hd+7870

But I decided that I might do a little (very little) video editing on it. Is premeir or a program like that require a 7970? Or with the 7870 be enough for someone like me who wants to build the cheapest but good quality editing/gaming rig? I'd like to stick with the 7870 if I can.

http://www.amazon.com/XFX-FX797ATDBC-Double-Edition-Graphics/dp/B006W3ZU4U/ref=sr_1_1?ie=UTF8&qid=1366026971&sr=8-1&keywords=XFX+R7970+Double+Dissipation

adobe premier uses cuda if i am not mistaken... nvidia might be an option  but if you are mostly gaming then you might get better value with amd