I was modelling quite a lot a year ago, so I can give you some pointers:
1. Your edge flow seem to cut of at places, see picture. Since I'm used to work with very low poly models, I'm extremely prissy when it comes to edge flow and edge loops.
2. This is a case of preference but here goes: modeling different parts of an object separately and them combining them might work in some occasions but it's really not something you want to continue doing, especially if you are going to animate the object. Since the vertices are not COMPLETELY connected, you might end up with ripping off parts of the model during the animation process.
3. Since you are going to use this for games, try lowering the poly count (which is essentially the number of faces) for a more efficient model. Like the volume/channel control panel, you could use bump mapping to create the desired details, same goes with the speaker.
Just my pointers, keep up the good work, you are great! ^^