I have both. The E11 is warmer. The E7 is more 'sterile' / slightly colder. It's the best way I can describe it. I don't use the word 'dark' - because I don't believe that term really describes my impresssion of them. I see others describing the E11 as dark - but IMO the term "warm" suits it better.
Here was my comparison - hope it helps:
When using your Ad700 with the E7 and the E11, do you feel that the E11 changes the overall tone of the Ad700 or simply makes it more full? I have Ad900 and I love the sound, I don't want it to change much.