Best TTS for Asterisk 11 on CentOS 5.7

I am looking for free text to speech(offline) service for asterisk 11.
I have installed asterisk on CentOS 5.7.
I have tried Flite, its working fine but dont have many voice options.

I have tried Festival,but while installing it gives following error,
CLI> “module load app_festival.so”

Unable to load module app_festival.so

I have also tried Cepstral with app_swift for asterisk ,
but unable to compile it as it gives error as “make: *** [app_swift.o] Error 1”.

Thanks,
Harsh