The NetVanta 7100 will support this setup. You would need to configure the new Internet connection and change your static default route to point to the gateway on this new connection. For the current Internet connection, that will just be used for voice, add static routes to the IP address ranges used by your voice service provider.
I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post to unmark it and select another in its place with the applicable buttons. If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.
I also wanted to link to this guide that can be used to configure failover between the two Internet connections in addition to Charles advice: