Have you checked out Synthesys yet?
There have been a ton of text-to-speech tools that have come out, using Google or Amazons TTS programs.... and they all sucked.
In fact, there have been many great video products that incorporated these, and when I did my reviews, I never even bothered mentioning that "feature", because I found it to be all but worthless.
But my tune has changed now, as Synthesys has come out, and actually provides TTS that actually sounds really good... and MILES better than Google or Amazon's TTS programs.
Take a look at Synthesys on my page, and HEAR the difference! I even have a comparison right on the page!