I always love the "order of importance" debate. On several occasions during my life, I sold high-end audio gear, and the advice regarding what component is most important varies from saleman to saleman, and store to store. At one time, I thought that the source components (turntable, CD player, etc.) were the most important, because no downstream component can correct for mediocre signal input. If that logic is valid, then you must also have components in the rest of the audio chain that are good enough to preserve the original signal. That said, the most problematic components in an audio system are the transducers, since converting one form of energy to another introduces all sorts of problems with linearity and distortion. Back in the good old days of turntables, tonearms, and cartridges, the signal produced by the cartridge (a transducer) was also subject to a variety of mechanical bugaboos, including vibration and resonance. Today, since most people have systems based on digital rather than analog sources, there is only one transducer in the system, the speakers. Speakers must be linear, have fairly flat frequency response, and have acceptably low distortion. Most newer preamps and power amps have low to virtually no distortion and are almost ruler flat in their frequency response (at least that's true for solid state models, and the best tube units), so the impact of the amplification units are lesser, relatively speaking, than the source component or speakers. This is a long-winded way of saying that my ranking, by way of importance is: speakers (the only transducer); source component; preamp; and power amp. Let the debate rage....
