I have a GTX 460 by Nvidia. Most games are okay on 24 inch monitor. But Youtube frame rates stink! I have an old quad-core cpu. I would think it would do okay for vids but it sucks. You don't see frame rate comparisons for video card for youtube videos.
YouTube frame rates are generally determined by internet speed. You want faster YouTube? Get faster internet. Two-dimensional video can be run perfectly by even integrated graphics with an old Core2Duo. Your hardware isn't the problem.