PGN specifically IIRC use Tok0voip (replace the “0” with “o”), but it requires a TeamSpeak server to work. I say stay away from it, mumble is almost the same when it comes to user experience and doesn’t need any third-party stuff.
pma-voice is a decent system that is based on mumble, so give that a try first. It also has very neat support for radios and phonecalls just in case you want to use those.