That sounds even worse than the "whirring" noise I was assuming "sirring" meant.
Hope we get this resolved.
At least the way it is presented to us, it sounds to me like you are searching for an "equally good" solution rather than choosing the best solution. I'm not knocking you for trying to avoid Tantalum given its issues as a conflict material, but as far as I have been able to gather from what we've been told regarding this issue... Tantalum capacitors solve the issue completely. That means you have
found the best choice already and are currently trying to find a more
palatable best choice.
EDIT:
@Grench: I've got an Onyx C67ML Carta 2 and love it; Chose that over the Aura One for Android.
-God Ginrai