This tutorial shows how to try out stereo and 5.1 surround sound effects.The Mono Audio Effects collection is a subset of the Stereo and 5.1 Effects. Those multi-channel effect groups have additional effects that relate to their extra channels. Here's how they work
There are a large number of different audio filters available in Premiere, from bandpass and notch filters, to reverbs and delays, to flangers and other weird things.