An inlet cooling system unit that is fluidly coupled to a gas turbine can include a filter module configured to filter inlet air, a chiller module configured to cool inlet air, and a framework. The framework is sized and shaped to define a filer module receiving region which supportably receives the filter module, and a chiller module receiving region which supportably receives the chiller module, the chiller module receiving region located below the filter module receiving region such that the chiller module is received below the filter module. Related gas turbine inlet cooling systems are also provided.