Is there a way to rename a sound card in Mac OS X?
The Sound Card’s name comes from the Device itself, which “publishes” its name. The operating system reads the name from there. I don’t believe you can rename it, but you can definitely go to /Applications/Utilities/Audio MIDI Setup and create an Aggregate Audio Device (with the names you want) and select the input/outputs of each.

For example, you can create your headphones like this: