I have a 1.5Ghz Mac Mini and the frame rate watching flash videos on any web browser(even HTML5) is pathetic and practically unwatchable.
If i were you i wouldn't try that hardware hack.
Instead try first MaTubes(
http://www.macupdate.com/app/mac/28608/mactubes).
With this you can watch youtube videos with ultra smooth frame rate.
For other video sites try Vlc's "open network" function.
