One more thing I need to address. Just because a person gets good results from a certain kernel setup, it doesn't necessarily mean those settings will work for you. I highly recommend testing different settings on your phone.
One of the best ways to test how much a kernel can handle is to start off slow. Turn the setting up slowly and run that setting for 15 minutes or longer. Some kernels need to be broken in so to speak. A kernel may be able to handle a higher speed but turning the ghz up too fast will probably result in a reboot, freeze up, or bad performance. Another VERY important thing to watch is the temperature of the phone. Heat is the enemy. Not only can it cause damage to your cpu, it can also cause battery damage and have other ill effects. Please keep these in mind when messing with your kernel.
Personally, I vary rarely overclock my S3. I've found a kernel set with the proper governor, I/O, etc will be more than enough to give great performance.