1st what ram do u have? I doubt it's gddr3 since that is used in graphic cards. So it's ddr2?
And for gaming u definately should upgrade the vid card.
"well if the ultra high you mean is doom 3's then no. even the newest cards have trouple with that setting, but high should be ok. you might have to put some things on medium."
I can play doom 3 on high settings (not sure if they were ultra high but I doubt it) with my fx5700. (eye candies off) So I think that the x800xl will do a much better job.