I've never heard of Gauntlet. If you want to experiment with GPU clock settings, MSI Afterburner
is your best bet.
As Masterchief says, it can be risky if you don't know what you're doing or if your PSU and cooling system aren't up to the job. Also, the fps gains are minimal, so it's usually not worth it.
Afterburner allows you to create custom fan profiles. This means you can set the GPU fan to be much quieter at idle, or you can set it to automatically increase the fan speed to keep the card cooler at full load, potentially giving slightly better framerates without having to mess around with the clock speeds.