How many watts of power do we really need? Well lets say that you buy two speakers that say they can handle 500 watts each and they are 8 ohms each. so now an amplifier that can do 1000 watts into 4 ohms is a good place to start. If you size the amp too big you run the chance of blowing speakers when things get heated up a bit in the performance and if you size the amp too small it will go into clipping before the required sound level is reached and you run the risk of frying speakers with square wave transients that they cannot digest. Personally I buy the amp with a max output a good bit higher than is needed and run a compressor limiter in a “brick wall” mode to stop the amp inputs from going past the best point. Be well aware that the amp output levels change according to the loading in ohms that you place on the amp channels and use the proper gauge wire.