Narkissos, I really like your reasoning concerning the realm of ideas. Is the concept of "metareality" applicable here?
Anyway, I never really believed in an afterlife and I consider myself a agnos-atheist as well.
I do however, have serious doubts about not living again. I mean, it has gone "wrong" at least once for me (being alive at this moment) so I think it's only reasonable that it will go "wrong" again after I die. Meaning that I expect my consciousness to be born again in a human being some time after my death. I do have trouble understanding how this would work in practice so I usually say it would take another universe for conditions to be right to produce another "you". Anyway, I do believe there are some possibilities in this direction of reasoning but I acknowledge that it's speculative to a degree.
Bas