The two 5 watt resistors are part of the output 'zobel' network.
It could be that your triac borad is tripped & shorted.
That would explain the resistor getting hot.
You should be able to disconnect the triac board.
It's o/k to test the amp it without it.
If not that, I would check the capacitor part of the zobel. (C 8 0.1 uf) or simply replace it.