I thought about the 64's, but I can justify paying that kind of money for a chip that is only barely supported, has no real application outside of servers and mass-compilers, and is so new in the personal computing world that support is shaky at best.
I'll just stick with the XPs. I won't throw any money into the "64bit money pit" until Microsoft's 64bit Windows version is solid enough, until PC games turn 64bit, until the hardware standard goes to 64bit, etc and so-forth...