Yes, you will need a v3000, v3001, or a v5000. The NBX100 does not support SIP mode.
You will also have to have the memory upgrade to run in SIP mode.
The NBX line either runs in SIP mode or NIP mode (Native).
If you are on a software version earlier than 6.5.x you will need an external voicemail server. Version 6.5.x included an internal voicemail server while in SIP mode.
Read the documentation on how to convert your NBX from NIP to SIP mode, as you will loose all custom recorded messages fro voicemail and for your auto attendants.