A 15A connection is physically different from a 20A connection. A 15A PC has a totally different connection than a 20A cord. Your equipment only has 15A connections, so you can't use a 20A cord with them. This in no way limits the quality. It's not a rating as much as it is a type.
15amp / 20amp PC's and Conditioners?
Another begginer's question for someone: If my amp (Krell 300i) and cd (Krell 300cd) recommend 15amp PC and conditioner,does this limmit my options in PC's and conditioners since some of them seem to be rated 20amps?