download problem

i used to have no real problems when i downloaded, but lately when i open a file, it will open in quicktime player. i want them to open in soundjam mp but now, ever since i downloaded a newer quicktime, the downloaded files all have a quicktime symbol next to them instead of a M3 symbol. what i want to do is to be able to launch the files so that they open in soundjam mp and not in quicktime.