Quality is not linear. In other words, in audio, products don't get a number representing its quality and if one product has a higher number, that means it's better than another product with a lower number. IEMs and Headphones have many dimensions. Usability, fit, comfort, beauty are all important dimensions as well. Even within sound, there are many dimensions such as sound stage, resolution, detail retrieval, macro and micro dynamics, timbre, etc and no headphone or IEM can be better than all other choices in every dimension. So, I don't think of levels the way you are thinking about it.
What I can say is that the C9 improves every product I've paired with it. Some more than others. The biggest thing it has done is made my IEMs sound more like my full sized headphones to the point that I don't miss them anymore. In fact, I feel that I am losing isolation when I put on the full sized cans. I think with the C9, I would almost live without full sized headphones. I may not travel with them anymore and use them only at home.