wow, nice setup&renders!
..a pitty that we can`t check rendering of that sound layer
Concerning the displacement the bit depth is important; just converting to 16bit before gives better results (maybe apply slight blur, too)
but also the base mesh should have more than two triangles, so by default in many applications you get a min poly count mesh for flat planes.
these should be sbdivided with evenly spaced faces.
btw. isn`t that room much too small for those speakers? ..for a setup like that the WAF is way out of scale anyway..

why not go for a more spacious scene with maybe a view to a nice landscape?
..and one thing I just (not)saw on the second look.. the cable mess!..hehe
To make it look real, IMO, you won`t get around modelling that stuff
cheers,
daniel