Is it worth it to get an xbox now when the Xbox 2 is coming out this holiday season? Not really.
Gamecube is dirt cheap and you still have a good 1.5-2 years on it before the next one comes out.
Prince of Persia and MK are multiplatform games, so that really doesn't matter.
Honestly, it depends on how much you want to spend vs the types of games you like to play. That's how you should make your decision.
"Give us cheese! What? No cheese? We're bombing you!" ~Daily Show
"Goverment is nothing more than a group of people ungoverned." ~ Shepard, Firefly