What kind of plastic? I imagine that in the near or maybe far future, 3D printing would make cabinets a lot more interesting while keeping all the desirable properties for audio production. I don't think you can 3D print MDF, but who knows what the future holds.
Marantz SR-5007 theater, Marantz 2325 stereo
Klipsch WF-35, WC-24, WB-14 theater, Klipsch Forte II stereo
Sony PS3, Xbox 360, Wii U