That's a nice o/c, but it depends what you're after. If you have to push the machine to see how far you can go, try 1.5 volts and 400 FSB.
Personally, I run my 6600 at 3200 because I have to use it for work each day and want a stable, dependable PC. And I don't find that my activities (data access, compiling programs, editing pictures etc.) benefit a whole lot by running at 3600 - especially with all the added heat.
Time some of your more common tasks at your current speed and then push the chip to 3600 and see how much faster they run. You may or may not be impressed!