Where you set your volume on your preamp has nothing to with whether your amp is running out of power, only the gain of your preamp.
Are you in fact running out of power? Your amp has a clipping light on it that will flash if it is. Is it flashing? Does it flash if you turn it up a little further? Where are the gain controls set on the 7100?
Are you in fact running out of power? Your amp has a clipping light on it that will flash if it is. Is it flashing? Does it flash if you turn it up a little further? Where are the gain controls set on the 7100?