definately not....you can cool it with liquid nitrogen if you want, but there is definately a limit to how high a clock can go before whats known as 'artifacts' appear on your screen. You watch, if you use ATi tool that is, it will get up to about 400-410 and stop because it will detect artifacts. I know this cause i have a Radeon 9800 Pro, with a watercooler block hooked up to it (best cooling solution available) and i can only get it up to 414Mhz core and 356Mhz mem before it starts detecting artifacts.
Now obviously i could keep manually overclocking it to anything i want (reasonable) and my water cooler would keep it cool. But the thing is, whats the point in having a 450Mhz core and 400Mhz mem if you cant see anything on your screen cause of all the crappy artifacts?????