daphy

Hi people,
anyone doing videoediting on a Mac?
I have a pre intel G5 machine dualcore 2 ghz, with 2Gb ram and was curious to know if it can edit HD quite rapidly. I've tried to paly an HD movie (300Mb) made with a canon 5D and it goes jumping instead to fluently run...horrible!
Can you please give me some advices? Better to implement the one I have or better change machine?
thanks