Hey Dna^Yay, the stuff you read no doubt referrers to transistor power amps, they drive/deliver different output power (watts) depending on the speaker load, (in general more into less) as in a (tranny) power power amp may deliver 80 watt rms into 8 ohms and 100 into 4 ohms and less (~50 watts?) into 16 ohms (i.e. more resistance, less watts to the speakers), as BDS says, tube amps (as they have an output transformer) are different. Also with transistor amps, if you put to little a load on them (e.g. 2 ohm) than they are designed for, you can damage them (suck the guts out of them). Another side of the coin though is the speakers, 16 ohm speakers have more windings (more electrical resistance) but they are thus more efficient and sensitive. Its all a balance, but rule of thumb is match both the speaker impedance/resistance and power handling to what the power amp is capable of/designed for. (it's actually not quite that simple in that speakers change their resistance /impedance with frequency and other stuff)