I thought it was about time for this question to surface again. I have all the cakewalk videos. X2 Explained is a great video. SWA mix clinic not so much. if you are going to choose between the two get X2 Explained. It is much better.
You should also look into SWA Complete Sonar X2. Karl does a fantastic job explaining Sonar X2, but I think the real strong point is all the time in the beginning he spends showing you how to set up your hardware, and setting up midi. I really liked the way X2 Explained was setup. Explained x2 and SWA Complete Sonar X2 are the two best videos for X2