Performance characteristics of video card in video editing rig

Looking to build a video editing rig and pondering how much money I should put into the video card - and of course, what card to buy.

The user will use Adobe CS6 Premiere Pro and Sony Vegas Pro.

Money is a consideration.

It is my understanding that at that version, only Nvidia CUDA acceleration is used. AMD OPENGL acceleration was implemented in CC (version after CS6).

So, what's important? Architecture? Professional quadro cards do a better job than the gaming cards? Memory bandwidth? Amount of VRAM? Will a $200 card perform 2x as well as a $100 card?

I've seen some articles over at Puget Systems' site, but they're 2 years old and wading through the Adobe forums is like being in the jungle in a fog.