You can either create a new station or add a mountpoint on the settings of your radio station in the Shoutcast Radio Manager.
Click on "New stream" under :
1- Shoutcast For Business users:
You can add as many secundary streams as you wish, including 64 kbps.
Note that in case of using Shoutcast's AutoDJ tool (the planner) you can add one mountpoint 64 kbps (AAC or MP3) only. If your main stream is already 64 kbps you can then create an additional one of the format/bitrate of your choice.
2- Shoutcast Server Software
You can add as many mountpoints as you wish.