Speaking more generally about one point — GPUs — how much a good GPU will help depends on what your timelines look like. Vegas has generally been good about being able to play back clips smoothly. Where a GPU can help is when you start scaling, compositing and applying effects — DEPENDING UPON how the application was written. I switched from Vegas to Premiere a year and a half ago, so I don’t know the current state, but I had found that Vegas produced incorrect results with the GPU support turned on often enough that I always had to disable it. Hopefully it’s better now. But many CODECS are not written to make use of the GPU for decoding/encoding, so you might not get an help there. If you’re not scaling and compositing much, you wouldn’t get much help. If you’re doing a lot of color correcting of clips, you might get benefit there. But for simply timelines, it probably would not have a big impact.
I’m evaluating an nVidia K4000 now, it’s made a huge difference in Premiere’s performance. In one project where I do a lot of laying a color slide on top of video with the color at 50% transparency, then add text slides on top of it, with color correction added to all the clips, the same computer went from very stilted, low frame-rate playback with all six cores maxed out to completely smooth playback with 50% CPU utilization when I put in the K4000. But, if it was just straight cuts with no effects, it wouldn’t have mattered. The built-in CODECs that come with Creative Suite don’t use the GPU, so there’s no help in encoding/decoding.