Hi-Fi Stereo Amplifier gain regulation with potentiometer
The usual approach with power amplifiers is that you have the volume control on the input, and a constant gain of the actual power circuit. This would mean putting the potentiometer on the inputs of the circuit. 

Also, the chip is not guaranteed to be stable at all gains, so if you adjust the gain in the feedback loop of the chip-amp, it might oscillate and start misbehaving.

If you connect the pot up front then you don't have to worry about wattage of the potentiometer, high wattage potentiometers are expensive.