Ok...the DLC doesnt download to a game disk. Example...rockband, if you download some songs, I have noticed that almost every RB game will use the DLC. I would imagine that if you have the Noble or Defiant map packs, they will still show up either way. I dont know about CEA tho. At worst, and it looks this way, you will have to take out the CEA disk, and put in the REACH disk to play the other maps. Frank did put out that in the future, the classic maps will be added as DLC for REACH, so you will not need the CEA disk to play them, you can use the Reach disk at that point. I believe that as of now, you will have to use the CEA disk to play the classic maps, and the Reach disk to play Reach MP. It really isnt a big deal.