I had a pair of CMC-20's for about a week, 5 years ago. The CMC-20's were very thin sounding I thought, and I returned them. The AT853's are so much better in my opinion. I'd say CA11/C14/AT853 are all more or less in the same league. Upgrade to any of them that you can find in EU for a decent price, and you will be happy.
If you get CMC-4's, or any other AT853, you almost surely want the "low sensitivity mod" (aka Chris Church's 4.7k mod). Otherwise they will overload on loud music.