The question is already quite long, with two different formulations. And I noticed that my own answer to my question is not 100% correct.
Consequently I would like the question to get some new attention. Now I could
What is the preferred way?
The general rule is: don't edit questions in a way that would invalidate answers that were correct at the time.
If all existing answers are incorrect or incomplete, we get into a gray area. On the one hand, we don't want to flood the site with duplicate questions just because they didn't get a good answer the first time round. On the other hand, if your question was systematically misunderstood or if you've realized you didn't express it clearly, it may be better to edit the question to match the existing answers, and ask a new question that covers what you really meant to ask.
If you realize after the fact that the question you asked was not the question you meant to ask, then, unless the question is unanswered, do ask a new question.
I think your case falls into the grey area. If you can find a significant difference between what the answers cover and what you want to know, then I encourage you to post a new question, linking to the old one and clearly explaining how the questions differ. On the other hand, if the problem is merely that your question hasn't had good enough answers, then all I can do is encourage you to give it some time (you don't have to mark any answer as accepted if no answer fully answers the question); you may try to hurry things up by offering a bounty (but keep in mind that bounties don't guarantee good answers).
