The BIPUs are discontinued so I wouldn't recommend them. If you are on version 5 software on the CIX, or can upgrade to it, then I would recommend the MIPU. Otherwise, the LIPU will do.
Both the LIPU and MIPU cards will work well with Netphone even for the external or remote Netphone. If you're a dealer, call the sales support desk and they can help you with the licenses stuff.