Extended kinetic equations, taking into account removal and generation interactions, and presence of a background medium, are considered in the discrete velocity formalism, and applied for studying the problem of a gas in a uniform host medium according to a planar 8-velocity model. After deriving the relevant governing equations, equilibria are investigated in detail for varying absorption, generation and scattering properties of the fixed, but in general not isotropic, background. Some stability properties and preliminary results about shock wave structure are also discussed.