You can do that. The only thing I would recommend is using a 60hz tone instead because most multimeters (unless you have a good one) are more accurate at 60hz. Also remember that setting gains with a meter isn't perfect, and if you listen to music on the system you will have room on either side of where you set it to dial it in. Make sure your voltage isn't dropping too much at whatever setting you end up at. No use in setting the gain for full power if your electrical can't hold up (for example).