OK, so what frequency? How do we determine the frequency when OP gets this all installed and if he is not measuring at the one specific frequency where his amp might actually see 2 ohm how is he going to estimate power?
The correct answer is he needs to set his gain by ear while listening to music if he intends this to play music, if he is chasing numbers he needs to set the gain with an SPL meter to find maximum output. This got over-complicated when OP decided he needed to figure out precisely how much power he is getting without understanding impedance of a loudspeaker system and without the willingness to buy the proper tools to measure real-time power.