iam pretty sure, if you would raise the voltage to 1,35v (which should not really be a problem at 110nm) and keep it cool on water 450mhz must be reachable

yes probably no problem for 110nm chips, but I'm not sure about the voltage regulators.
Covers the Waterblock also the VRs? On GPUs is that very important.
Buck converters have no problem doing something like 0.8 to 6v at full load current. Just duty cycle on FETs change.. or diode if not a synch buck