I fail to see why it makes much of a difference at all what order you use for turning equipment on and off. If you're worried about power-on transients, simply turn the volume pot on your preamp all the way down while turning the equipment on and off...
The procedure Loomis described is correct. Obviously, the importance of adhering to that procedure will vary depending on the design of the particular components.
Turn-on or turn-off transients may be generated by preamp circuitry that is "after" the volume control, those transients therefore not being affected by the volume setting.
Also, with respect to source components, it is conceivable (although probably unlikely in most cases) that it may be unhealthy for a preamp input stage to be repeatedly exposed to transients from the source components that exceed its internal dc power supply voltages (voltage "rails"), which would be zero when the preamp is off, and therefore exceeded by ANY transient.
Also, given that the preamp is turned on first and off last, turning the volume control down when source components are turned on or off is good practice, to eliminate the possibility of a similar effect occurring at the power amp inputs.
Finally, it should be kept in mind that many power amps may continue to be able to amplify transients that appear at their inputs for a considerable number of seconds after they are turned off.