You want more power if you want to experience full dynamic range without clipping. What you are not appreciating perhaps
is that any music, jazz or rock included, or movie soundtrack with wide dynamic range will require sudden short large swings in power ten to 100x times more than what you are coasting along with most of the time. Most people don't realize that their amps are clipping and distorting albeit only briefly. Basically if you want cleaner unclipped sound you need more power on reserve.
Another classical loving friend of mine uses a 40w 2 channel amp to drive large Meadowlark floorstanders. I've gotten used to him running up to turn down the volume during climatic passages. He says he prefers it lower and I haven't mustered the courage to tell him its because that amp clips too often with those large speakers at any higher listening level.
From a psycho-acoustic perspective, the distorted sound from a clipping amp is perceived to be loud. Let me give you an example regarding one of my brothers, who visits from L.A. every few months. He annoys my wife in that he keeps raising the volume on my gear way over what I would because it doesn't sound "loud" to him ie. distorted. I know that he uses an older HK 5 ch receiver with a "rated" 80wpc which whenever I hear it I have to turn down too because its butchering loud transients which I find irritating and sounds "louder" though it is not.
The point on the RF and heat is that its outside of the box and cannot influence the processing circuitry. The pre-amp processes the signal at low voltage which is more easily corrupted in the same box as a large transformer. The better receivers minimize the problem but can't eliminate it, unlike separating the amp from the processer.
Also remember that S/N ratios are only part of the picture and need to be referenced to something to be meaningful. Many manufacturers quote them at 1 watt which may be much different at another wattage or full power. Some of the numbers including rated power thrown around by several well known receiver companies have been shown to be very misleading over the years.
