You’ve confused gain (and input sensitivity) with power output. They are two completely different things. There’s no way to calculate power output in watts from the information the OP has provided.Input sensitivity, gain and power output are all related mathematically and you can work out one from the others if you assume a certain loudspeaker impedance.
I didn’t say the system would be capable, just that an 8Ω speaker driven by the maximum output voltage would need 2500W from the amplifier and need to be able to tolerate it.