I find this: "that can't play fullscreen video" quite strange. I have no problems with fullscreen videos (~5% cpu), or multiple windowed ones on a 5yo cheapest unknown-local-company laptop. Are you sure your configuration is not broken in some crazy way?

Not saying that you shouldn't update, but this is not what a 5yo laptop of any kind should behave like... If you do the same thing to your new laptop, it might not be worth getting it ;)