Can I use my Prosody X card as my system's NIC?

Yes. The Prosody X card contains a NIC, which you can used as a replacement for the standard NIC. However due to the Prosody X card's architecture, it does not work in the same way as a standard NIC.

The NIC on a Prosody X card sits behind a built-in Ethernet switch on the Prosody X card. The upshot of this arrangement means the NIC on the Prosody X card will only receive broadcast packets and packets addressed to it's specific IP address. This means that when the Prosody X card NIC is used with a packet sniffer, it cannot be setup to read packets which are destined for other IP addresses.