I don't understand. What is your objection to the stand-by idle of class A amps? I'd like to learn. At standby my Levinson draws 2.4kw/day, about $.40 where I live. Please explain.
Low bias amps or amps with a "special" power supply like the Sunfire's will sound the closest when going from "stone cold" to "fully warmed up". Since the Sunfire's and other similar amps are highly efficient, you would not really notice ANY increase in your electric bill if you were to leave them on all of the time. While the Sunfire might not suit your tastes, i simply selected it because it is a relatively beefy amp and is well known. Sean
Kind of guessing why you would want to cold start an amp. If operating costs are an issue, I side with No $. If it's from an eco friendly perspective, consider that the idling provides heat. In the upper midwest we need supplement heat for approx half the year. It's slightly higher $/btu for electricity but so what. If you live in Cal, well then turn everything off to avoid brownouts and surges.
Another consideration, cold starting amps tends to be more stressful on their components. Especially for tubes.
While opinions vary on the topic of "on vs off" and life expectancy of gear, i am a FIRM believer in leaving amps & preamps ON all the time. My only hesitation for "always on" is something with an LCD display such as transports, tuners, etc... that will "burn out" or tube type power amps where they are dissipating a lot of power at idle. Otherwise, there is more damage done to equipment due to "inrush current" than there is in letting it idle so long as the unit has more than adequate ventilation. Sean