Sorry it's been so long since following up on your question, but I've been too busy to monitor this sight for a while.
I don't know anything about 4-channel sound in MEP, so I posted your question on the other Magix user forum. You should put this forum in your favorites because it's better than this one, even though this forum is pretty useful, too.
Hopefully, there is some information in there that will help you. If not, feel free to register on that forum and continue the discussion. The people who monitor that forum have incredible expertise.