Um. I'm pretty sure the only water cooled G5s were the Dual 2.5GHz, Dual 2.7GHz (both single core, dual CPU) and the Quad 2.5GHz (dual dual core CPU). The service manuals confirm that I am not going insane. Are you sure you have a dual 2.3GHz and not something quicker?
PM me the serial and I'll look it up for you......