That's a great question. Probably the best way to modify your voice is to use SSML tags. Three SSML tags in particular might help you to achieve a stronger, more excited tone in your voice. These are pitch, volume, and emphasis. It sounds like you may have tried pitch, but it's possible that you set the pitch to low rather than high, which might have created a more masculine sounding pitch. Here is an example of these tags in use:
swift -n Allison "Thank you for completing the task. <emphasis level='moderate'><prosody pitch='+40%' volume='loud'>Good</prosody> <prosody pitch ='+25%' volume='x-loud'> job</prosody></emphasis>"
You can read more about using SSML tags on our SSML tutorial, located here:
http://www.cepstral.com/en/tutorials/view/ssml