I'm going to do the same if my pl11 goes kaput..I moved from a PL11 to ES18 and believe me it wasnt much of a downgrade. So I doubt PL11 will be a better one.
Like above I also suggest E10, or if you can E10M . Heard a good deal about it
M2 has more congested sound compared to C-12 , both have almost similar amount of bass , C-12 is more laidback / warm sounding and suited for instrumental etc compared to M2.
I'm going to do the same if my pl11 goes kaput..
So what's the difference between them.. What do you feel is cut short