I'd balance what Chess said with several points:
(1) The actual total power consumption of the stated components in the conditions under discussion is likely under five watts. It's unlikely you'd leave the volume cranked to max and leave the room for hours.
(2) Repeatedly power cycling electronic components likely decreases their life span, at least to some degree. There's likely wide variation depending on age, type, ambient conditions, etc. Whether this is significant for an individual case is virtually impossible to predict. However if a controlled test and statistical examination of thousands of units were done, IMO there would be a lifespan difference, at least under some test parameters.
(3) If the statistical lifespan is decreased even slightly, that increases the environmental burden of disposing of the failed equipment, some of which contains toxic materials. You'd have to balance this cost against the alternative of leaving the equipment on.
(4) If you want to make a meaningful improvement in energy consumption, other very effective possibilities exist. Proper home weatherstripping and insulation, or just ensuring proper vehicle tire pressure can save significant energy and associated environmental costs. E.g, if most vehicle owners simply used the proper tire pressure, this would save 1.24 billion gallons of gasoline per year, just in the U.S.
Personally I don't leave equipment powered up all the time. If I'm away for a few minutes and may return, I leave it on. If I know I'll be away for an hour, I turn it off.
