It depends. I've noticed that sometimes my AT&T cell calls are of a higher quality, depending on who I'm talking to. I think this has something to do with their

It depends. I've noticed that sometimes my AT&T cell calls are of a higher quality, depending on who I'm talking to. I think this has something to do with their HD Voice product. I like it, the quality reminds me of what I've experienced in the past with the Cisco UC platform on a well-provisioned network and UC platform. The goal of Skype, Viber, etc. are to always give you some level of audio across all networks, so the codecs they are using have a different goal than Cisco UC. All these codecs have low bandwidth requirements, much lower than what you have. If you have a residential ISP, QoS might be an issue with some of the higher sampling rate codecs, but you probably won't notice them with Skype. Try running an open source VoIP MCU at home on your LAN to see how good it could be.