A Kenwood TS-50 ham radio made back when the 2SC2879 was still a new part used two of them to get 100 Watts peak. The Toshiba published data for this part claimed 120 Watts peak per transistor. Two of them held down to 50 Watts each are pretty rugged, and will mostly shrug if the antenna SWR gets too high.
Four of them delivering 500 Watts is pretty well on the money for what Toshiba claims for it.
Then again, folks who fancy what they call "competition" performance will obtain this by boosting the power supply voltage above 13.8 Volts.
There is a relationship between power-supply voltage and amplifier output called a 'square law'. This means that if you were to double the power supply to 27 Volts you would see four times the power, or 2000 Watts.
In real life, this wouldn't be for very long. Certainly not long enough to snap a picture of the wattmeter. Probably not long enough for the meter needle to travel upwards.
But if we only increase the power supply voltage by half-again more than 13.8, this is around 20 Volts. The square law says that we'll see about double the wattage we did at the lower power supply voltage.
The Toshiba transistor was made for so long and in such quantities that the quality grew really high, and the abuse that it could take was equally high.
Running it from 20 Volts counts as abuse for me, but your mileage may vary. Not so different from putting a nitrous bottle on your daily driver. But the life of that engine will no doubt be reduced, compared to operating it at stock rated power.
Newer parts from other suppliers are all you can buy since Toshiba quit making that part for good. None of them are as stout as the original Toshiba. How much 'competition' abuse they can take is an open question. Mostly you find out when they go "snap!".
It's worth considering that what the receiver at the far end of your conversation will hear if you double your power.
S-meters vary a lot from one radio to the next, but doubling your power will show between one-half and one whole S-unit on the meter. To me, that doesn't seem worth blowing up an amplifier with the nitrous treatment. People get excited when they see a wattmeter increase by half-again, say from 500 to 750 Watts. Looks like a lot on your wattmeter, but it's still kinda far from double.
YMMV.
73
