I cant speak for the 3060, but my 2150s don't get super hot. They are class A, but dynamically adjust the bias current to match output levels.
The differentially balanced 2150 is said to be class-A biased to its full claimed continuous power output—1000W into 8, 4, or 2 ohms—by means of a circuit that continually adjusts the bias current based on voltage output, current draw, and load. Boulder claims that this operation is performed more quickly than the speed of the audio signal itself, which means that the circuit can maintain class-A operation when confronted with a taxing musical transient, after which it gently lowers the bias until it senses another peak (footnote 1). The 2150 can thus provide the positives of full class-A operation that's free of crossover distortion, without the negatives of massive power consumption, excessive generation of heat, or, Boulder claims, the audible "steps" produced by other kinds of active bias-management systems.
Footnote 1: Unlike an amplifier with a traditional class-A output stage, the Boulder 2150 runs relatively cool.—John Atkinson