Yes, STEREOPHONY is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, E 1, R 1, E 1, O 1, P 3, H 4, O 1, N 1, Y 4.

Is it a valid word?

STEREOPHONY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

reproducer in which two microphones feed two or more loudspeakers to give a three-dimensional effect to the sound

Also: stereo system, stereophonic system.