definitely Gentoo!
it merges with your machine into an unbeatable piece of hardware!
besides that, the portage updating system rules!
the only thing is that it's not an easy install, but if you follow the handbook it shouldn't be a problem.
final remark: If you can, go straight for the 2.6 kernel install (not the 2.4); much better hardware support, performance is smoother, etc etc etc
oh yes! And Ac3d runs sweet in Gentoo
just finished up configuring Povray for it.