A cost-effective way to expand the capacity of HFC networks is a most efficient use of the amplifier power. The maximum output level of components is limited by the non-linear behaviour. In the current practice, 2nd (CSO) and 3rd (CTB) order non-linear behaviour is thought to limit the performance, and thus the maximum signal load. Studies of the ReDesign project though, shows that in case of digital loads the performance is not limited by 2nd and 3rd but by 4th and 5th order non-linear behaviour. In this paper we present proof for the above, followed by a first specification of the 4th and 5th order non-linear amplifier parameters. To conclude we show and discuss the match between the measured performance of an amplifier and the simulated performance using a 5th order non-linear component specification.