I believe the logo must be totally simple and remarkable, that is easy to remember and reproduce somewhere else. I think the logo should be just a letter D with some high tech font and maybe 1 or 2 vertical line(s).
Some options:
Ď ɖ ɗ ʠ Ԃ ԃ Ժ Ⴛ פ Ⴇ ᐅ ᐉ ᐈ ᐷ ᒇ ᗠ ᗫ ᗬ ᵭ
Ϫ Ҳ Ӽ Ӿ ೱ ᅕ
My favs:
ᗫ, Ӿ
e.g. ᗫ5.0, Ӿ5.0
I think the X is interesting, plus it gives homage to Xcoin