Reply-by-SMS with Google Voice
You should be able to go to 
Settings>Manage Applications>All Applications>

Go to your MMS.apk, and reset the defaults. 

So long as you already have Google Voice installed on your phone, 
The next time you try to use this feature, it should ask you which one you want to use. 

But IDK- No JB love on the HTC Sensation, yet.