If you want one for speed and power, then I'd go for the new Athlon 64bit processors. However, to get full preformance out of it you will need to have a 64 bit OS. I think Windows has one, bug I'm not sure if its out yet for xp.
Apple and IBM jointly developed the PowerPC G5, world’s first 64-bit desktop processor. With two double-precision floating-point units, advanced branch prediction logic and support for symmetric multiprocessing, the PowerPC G5 processor builds on previous PowerPC designs, combining an optimized Velocity Engine with a superscalar, super-pipelined execution core that can execute more than 200 simultaneous in-flight instructions. This high-bandwidth core has over 12 discrete functional units that process massive amounts of instructions in parallel.