With my video editing, I often play two simultaneous 1080p 60fps streams. My system is an i7 860, 4gb RAM, and ATI HD 4650. The video is often jerky in playback. How can I improve play back and hopefully also get gains in Premiere Pro CS4?
I would personaly go with an Nvidia GPU. Adobe supports Nvidia's cuda video Acceleration thingi.
basically, you take the stress from the CPU and put it on the GPU.
I would recomend something like a 200 series GPU from Nvidia, maybe a GT240 1gb GDDR5, they are runing for $100 in newegg.
I would not recomend a 400 series GPU because i read somewhere that they don't official support it just yet.
Hope this helps