The Superstack is a kind of Tuning Kit for the Kronos. It provides specially designed Layerstack multisamples to make a single Program Preset sound fat like a Combination.
These „Superstack“ sounds are created by using analog and digital synths together with acoustic and electric instruments. Be prepared for 50 multisamples and 100 stunning Presets. Together with a decent Controller programming for Control Knobs 1-8, S1 and S2 Switches, Ribbon, Joystick for each Program Preset.
More details here