You may want to do some more research on AMD processors for Vegas. The 8 core would be the only AMD CPU I would consider at the point of this writing. Waiting until January might be a good thing to consider, since with DDR4 emerging, we are talking about a major increase in memory bandwidth over ddr3. PCIe4.0 is not expected until late 2015. I would wait until the next round of boards that emerge with ddr4, because there will most likely be a new round of processors from AMD designed to handle the increased memory bandwidth.

Upgrading a single component will not improve your system noticeably, unless your hardware configuration is severely limited by low cost components like slow GPU and slow cpu/memory speeds. Upgrading the triangle of components is how I tend to look at upgrades. PCI version/chipset -> Memory speed/bandwidth -> CPU. Optimizing your GPU interface with your motherboard PCIe version, pretty much dictates the level of GPU your current system can handle. PCIe3 GPU pretty much means the designer expected that much bandwidth available to the card, even though the card supports legacy modes. Legacy mode operation has more to do with selling GPUs than performance. X99 is not a big deal because of 6-8 HT cores, but because the 8 cores comes with more memory bandwidth and more PCIe lanes.