Someone breaks into your bedroom and steals only the items you have mentioned from the entire house? It is indeed someone you know or someone familiar with the yard / house. I would set up a camera in the room to record every persons face that appears at the window. Go to a shop and pick up some empty packing boxes for some subs and amps and leave them in your room again. Weigh them down a bit to make it seem like there is something there. Scumbag thieves...