radtek:
Ignore all "dynamic power" ratings (at 4 ohms, 2 ohms, etc.) for A/V receivers not just from Onkyo but other brands as well. It's a very misleading and useless spec because the dynamic power rating is measured in milliseconds (that's a few thousandths of a second). So, sure, it may deliver 210 watts per channel into 4 ohms for a couple of hundred milliseconds (1/5 second), or perhaps even a second, then it will overheat and the thermal or current-limiting sensor will shut it down.
Look for a continuous power-output rating into a 4-ohm load, perhaps just at 1 kHz with one or two channels driven.
Regards,
