Yeah, that's it. If you want to use Phoenix add Miner=Phoenix (capitalization doesn't matter) in miner.cfg. You don't need to add anything for poclbm, if the entry is missing it defaults to poclbm anyway.

Obviously, have the Path entry to phoenix.exe on Windows or phoenix.py on Linux. On Linux you may need to chmod phoenix.py to make it executable first, CP will get access denied errors otherwise.