It really depends on your internet connection and the software you use to stream. If you are using an Intel processor, then you can stream at higher resolutions in high quality as most of the Intel graphics cards can take advantage of OpenCL acceleration. For Nvidia hardware, 1080p is the highest supported resolution because they don't have OpenCL support for their chips. They do offer SLI (for a second GTX). So if that's your situation and using HD streams then 1080p might be fine. On top of that, there are other factors to consider such as how much RAM you have free when streaming and how fast your disk speed is vs network speed; which could affect performance greatly.