For you to be able to use the custom Siri sounds you'll have to backup your own default sounds first. If you wish to do so then go to the following path on your device
using either SSH/iFunBox/any other filetransfer program : System/Library/Audio/UISounds , then move the following files to a safe place either on your 
desktop or dropbox:

jbl_begin.caf
jbl_cancel.caf
jbl_confirm.caf
jbl_no_match.caf

After you have backed up these files you will need to go to /var/stash/Themes.xxx/Stevi Sounds  and then copy the files on there to the following: 
System/Library/Audio/UISounds

If you dont understand what you are doing and you dont want to maybe mess up your phone then do not even try.
(If you know what you are doing then there is no way for nothing other then replacing the sounds to happen)

