Hey ELS, sACN and ArtNet are in fact two different network protocols. Each has their own benefits and drawbacks. If your MPC computer needs access to a network or the internet, I would recommend using sACN.
In Settings -- Menu -- Network, enable sACN on your network card. Set up an IP address and Subnet mask. Hook the ethernet cable from the computer to the Pixlite. Configure the Pixlite with a different IP address, and the same subnet. And you should be good to go there.
If you choose to use ArtNet, last time I tried, MPC was locked to the use of IP 2.xxx.xxx.xx and a subnet of 255.0.0.0
As a result, the IP scheme for ArtNet here is not normally compatible with standard consumer network hardware, and there fore may not work with existing infrastructure. If your computer has a second Lan port, then this wouldn't be an issue.
In Settings -- Menu -- Network, enable EtherDMX on your network port, then switch over the EtherDMX tab, and set settings accordingly there.
Ignore any talk about loopback adapters in this post. You have no need since the Pixlite device is external.