Just looked up my test notes for the ACA build I did, at 24VDC supply (linear regulator) and 1.35 amps bias, that gives you a power dissipation in the output stage to be 32.4 watts per channel - so 65 watts in a stereo chassis. The temp of the heatsink (enclosure supplied with kit from the DiyA store) immediately above the output device was a comfortable 55 degC.