I just tried the YouTube plugin, it's really great! but it couldn't force 240p (I have a slow internet connection so i need to have this low quality option) and there is a keepaas plugin for chrome too [1] it even has a version for Firefox! but from what I read in its description, keeFox is the better addon.

[1] https://chrome.google.com/webstore/detail/chromeipass/ompiai...