I have a 400 square foot garage that I'm converting into theatre room. It already has existing walls with insulation. I really don't want to build a room within a room. So I guess what I'm asking is, is there another way to sound proof it with out building another room inside the room? I have looked at quiet rock and green glue but there are so many mixed opinions and not sure what to do. I don't want to spend a lot of money on the room. I am on a budget though I don't want to spend over a grand on it if possible.