d2girls
... do 20ampre power cords use a special type of plug to connect to your mains?Yes, 20A cords require a 20A plug rather than the more common 15A plug. You can Google it for a photo.
Does that mean that the new ref ARC amps are not useable with my normal outlets at home?Not exactly, because the preamps don't draw 20A, or anything close to it. So you can use a cord with a 20A IEC connector on one end and a 15A plug on the other.