I am assuming what you are asking about is the computer graphics card. I am not familiar with Vegas, but with Final Cut, the NLE does not really benefit from a graphics card upgrade. All you need is something that will allow you to see what you are doing in your NLE. As you said, all you will be doing is strait cutting.
What you do need is an I/O device, such as an AJA Xena (if you’re on PC), Maxtrox MXO2, or BlackMagic Design card. Those allow you to output to a broadcast monitor or TV, and that is essential in a proper edit bay
