So we just picked up a new PS6100x and I'm wondering if I need to setup the ethernet channels myself or is it automatic?
It's configured in an HA setup; dual controllers connected to redundant cisco switches with a 10GE interconnect. On the controller, I've enabled eth0-3, each with it's own IP 172.16.0.50-53, and a group IP address of 172.16.0.10. Do I need to bond the interfaces on the switch or will the controller take care of this for me?
You do not need to bond the interfaces. The iSCSI initiator on the host will load balance across all 4 nic's if setup correctly. Failover will be handled by the controller.