For the most part, you will not see a major difference in performance. For the most part. If you use Pinnacle Liquid Edition or to a lesser degree, Pinnacle Studio 9, there will be a performance increase in GPU renders and in the number of layers you can playback in real-time. Also, Hollywood FX 5 will benefit from a better GPU and 256MB of memory.
You may see performance gains in playback of rendered videos such as High-Def, but that is at the top of the spectrum in 1080p. For more detail look for the WMV-HD benchmark thread in the Video forum started by Dapunisher.