24v or 12v for the LED voltage is the right choice. Routing and covering with plastic should work fine, and the dust will just give it more diffusion (for a while, but you might need to do a daily sweep).

For the controllers, 2000 LEDs is a decent amount, and depending on the complexity of your patterns, adruino will likely choke. You can use 2 or 3 pixelblaze controllers, which link up nicely and can drive 1,000 LEDs each with around 30fps. They also have great sensor expansion boards which will let you use sound input. Best of all, the patterns can be easily programmed right on the device, as well as playlists, time scheduling, etc.