Assuming you are looking for Current (Amps) output of the amplifier, a quick approximate calculation may help: Power (Watts) = Current squared (I) X Resistance (R). Thus, I = Square Root of (Watts/R). Say the amp is 200 watts and you are driving into 6 ohm speakers, then: I (Current output) = Sq. Root (200/6) or 5.77 Amps at full output (200 watts). The formula is approximate because with audio we are dealing with AC signal circuits, not merely DC.