If you don't like the eSpeak voice You can always buy the
$1 which are very high quality and support a lot of languages. I use Vocalizer myself since it's bundled with MacOS and iOS. A free alternative to Vocalizer are the Windows SAPI voices which you can choose in NVDA, but don't ask me how to do it since I don't use NVDA myself; I only know this because I've been thinking about switching to Windows and have been researching my options.