From my experience, the bottle neck is the WIZ820. It starts missing packet when going over 9 or 10 universe with LightJams (which only refresh affected universes).
I need to drive 16 universes, so for now I ended up, turning my BeagleBone Black into an ArtNet node with code inspired by natcl's Artnet library. The ethernet performances are way better. When the Beaglebone receive the Artnet packet it validates it and send it via Serial to the teensy which in turns drive the 2688 led pixels via the OctoWS lib. It's working great, but I'm not too found to wait 2minutes for the Beagle Bone to boot up and would be happy to cut the middle man.
Is there any way to improve performances with the WIZ820 ?
I would be ready to split the task to multiples teensies but I'm not sure how it will work: It seems with the current Artnet code, Lightjams falls back to "broadcast" mode (instead of unicast) so it sends all packets to all nodes. So I'm afraid all nodes will choke on the amount of packets.
Thanks, I'm really enjoying this thread.