Agreed. There are a couple of other factors to consider. The speakers rated efficiency and listening distance will contribute to required power. My speakers are rated at 88db efficiency measured at 4 ohms and one meter, driven at two watts. (Since it's a 4 ohm spec, the equivalent sensitivity at 8 ohms is 85 db at one watt input). My listening position is about 12 feet away and power requirements at a given spl double for roughly every additional meter distance from the speakers. I need about 97 db output at the speaker to achieve the stated 88 db efficiency cited in the speakers specs when sitting in my sweet spot. Wattage doubles with every 3 db increase in SPL, so in my sweet spot, I need 16 watts of power output to achieve the rated 88 db in the specs.
88 db is relatively loud, but life like rock n roll spl often exceeds 100 db at live venues. The 12 db spread from 88 to 100 db requires a four fold increase in output power, or in my case, 256 watts to achieve when compared to the 88 db at one meter spec. I was not happy driving my system with a 100 watt amp. However, 100 db is also almost painfully loud (as is some live rock n roll).
