Is it realy ever worth it to overclock a 64 bit to the max and if you did, what would you need to keep it cool
As worth it as a standard 32 bit chip, nb: the a64 is a 32bit chip with 64 bit capabilities. A decent air cooler, water, or frost.
I routinely run at 2.4GHz without much effort. I run into problems due to my disk controller after that. If it wasn't for that I could go way higher I imagine. My temps are around 32/42 (idle/loaded) at 2.4GHz on air, so yes... it's well worth it.