Just a short video comparing the performance of the Power Mac G5 performance using different storage solutions. This may help you decide whether to upgrade your machine or not.
The boot performance is almost the same using any solution:
HDD - 53,88s
HDD RAID - 51,30s
SSD - 47,28s
SSD RAID - 45,38s
(measured from the startup chime until Flux kicks in)