Image forming system having enhanced functionality

A sheet feed apparatus, e.g., coupled to an image forming apparatus, can include: a main frame; a storage unit mounted on the main frame and configured with a capacity to store a large quantity of sheet-like material; a transporter mounted on the main frame and configured to supply the sheet-like material to the image forming apparatus; an additional unit adapted to be mounted on the main frame and operable to enhance a functionality of at least one of the sheet feed apparatus and an image forming apparatus; and a supporting frame mounted on the main frame in place of the additional unit, and further adapted such that the additional unit is mountable thereon; the additional unit being mounted on the supporting frame.