well, I'm not sure some of those features will ever be supported. And later G5s are just as fast as P50X0, plus they have Altivec, which the P series chips lack completely.
Completely for now.
Later revision of the core they are based on will have these instructions, so successors to this chip will feature AltiVec instructions.
And the P50XX is a much cooler running, lower power draw chip.
That being said, I have two G5s.