Not clear what configuration you are requesting, but neither is possible. It is not possible to use Era 300’s as front speaker in a Home Theater configuration, and Era 300s used as surrounds require an Atmos capable source, and the Amp is not Atmos capable. 

i use era 300 with apple tv 4k and works fine. my problem is that the sound quality of arc and beam is not good enough. so I would like a more convenient way to connect the era 300 to the TV. On Apple TV, you have to choose separately where you want the sound each time. I have 2 x era 300 and sub.

You’re using Airplay?

What do you mis in sound quality with the Beam or the Arc?

arc and beam are not in the same category in terms of sound quality. I would gladly replace Arc with 3x era 300 and 2x era 100 and a sub is not even necessarily needed. the contrast is glaring... era 300 as a surround speaker is a waste of quality when they have a better sound than soundbars. I want to use era 300 as frontpeakers.

…..i use airplay 2.

AirPlay 2 from an Apple device to a non Apple device will always be stereo, so you’ll lose any potential 5.1 aspect. 

5.1 doesn't matter to me, the problem is that era 300 sounds better without arc or beam. that's why I returned them after trying them on.

my system is primarily for listening to music and secondarily for watching TV/movies