What you are requiring is an audio power amp capable of delivering 240 watts. Or slightly more.
Since your power supply of 120 Vdc is insufficient to provide the 320 Vpk-pk required by a 120 Vrms sinewave, you'll have to use an autotransformer at the output to elevate the 42 Vrms from the amplifier output to 120 Vrms
Alternatively, you could boost the 120 Vdc to 320 Vdc, but that would be more complex and dangerous.
I'm assuming theoretical, lossles output transistors. Most likely the voltage would have to be aprox 10Vdc higher.