Funny how people differ. For me, he last to go would be greatest hits collections and various artists comps. Why? They often contain stuiff that's not available anywhere else, and go out of print rather quickly. They are often the most expensive things on the used market for that reason. But, the bottom line is having lossless. As far as i'm concerned, if all you have is lossy, you don't have a collection. The sound isn't all there.