> To keep the cost down, the top cover is aluminum-formed instead of CNCed

Forging is in no way inferior to CNC, on the contrary, a forget aluminium part should have more rigidity per unit of thickness, depending on the alloy.

I guess, you got to volumes big enough to open the mould for forging?

If you need an audio engineer, I can refer you one fellow. He worked at Apple, Harman, Asus, BBK, and is now looking to relocated from the East Bloc.