Might be able to help there.
I only selected IVONA 2 Russell - Australian English male voice, installed it and added the patched dll.
(Note that even if running x64, there's only a patch for the x86 voice, still works 100%) Follow instructions on the torrent info page.
I opened the speech settings in Syn and the voice was in the dropdown list
BTW, head over to their home page
, you can demo the voices there, then simply the select the one you want download on the torrent (reduces the massive download to around 250MB).