Hello my friend DoDo made almost 5 years ago Quad Pokey board upgrade.
For real Pokey chips exactly like Stereo but Quad (16channels) as it was in Atari Arcade.
He never finished it(I dont know if). He moved to another city lot of work in new job etc.
Maybe T0ri, X-Angel or Candle, Lotharek can finish it.
VinsCool told me He is working on 16channel RMT (also 16bit 8ch or 12ch in 8/16bit mode).
So there will be possibility to replay on PokeyMAX QUAD or on this board.

For fans of real chips, for Atari community (backup) here is first version gerbers:
https://matej.space/RETRO/POKEYSONIC_v01_RevA.zip

When anybody will make new version from this please include (original design by DoDo).

Its all I have.