I forgot to answer this:
i don't understand if doing graphics is hitting the cpu or not, ot if having an agp card will alleviate that. i am also synthesising sound too. thanks all.
Graphiccards these days are heavy optimized for 3D but they are just helpers for your cpu(s) so generating graphics will hit the cpu in any case. While most of the workload of 3D stuff is done in a graphiccard like Ati or Nvidia (when the drivers work well), 2D like videoprocessing is mostly done in the cpu. In general its a matter of experiences and what are and how do you want to archieve your (artistic) goals but I guess you got a pretty rig there so start to make your own experiences which money can't buy.
Cheers,
Malte