Gain pots in audio circuits are usually logarithmic taper not linear.
If the pot still works mostly, you can verify linear vs. logarithmic with an ohm meter. A linear pot will read ~1/2 Rt at the mid point. A logarithmic pot will not be anywhere near 1/2 Rt at the mid point (typically 10% or 90%). See the following link for more info on taper: http://www.resistorguide.com/potentiometer-taper/
Most modern audio circuits put only a small amount of power through the control pots. If the pots still mostly work you can get an good idea of the power rating by intentionally burning them up with an adjustable voltage supply. Rotate the wiper to one end and attach the power supply between the wiper and the other end. Increase the voltage while watching the current and when the pot starts to burn out you’ll see the current drop. Then calculate the power that burned it out (W=V^2/R).