While I’m not at all an expert on graphic cards…I’m just a user like you, trying to get the best card for Vegas. My months of research lead me to believe that Vegas does not take advantage of the newer segmented CUDA configuration on newer graphics cards. Therefore you can have a new card that has 1200 cuda’s in 4 segments…and Vegas will run slower…because it’s only use 300 cuda’s from one segment.
I would totally check your graphics card…suggest using high end older card if your new card has segmented Cuda’s.
If anyone else can shed light on this subject…I’m all ears…wanting to build a new system for Vegas…but haven’t heard any news on whether Vegas is going to refine their use of current graphic card technology?