Your Denon 3805 is an INTEGRATED amplifier & additionally has a radio tuner. An integrated amplifier consists of both a POWER amp & a PRE-amp. The POWER amp does just that; it produces the power. The PRE-amp can be called the controller. Its' knobs do the finesse job of selecting the switching & current levels which affect signal strength & volume from the speakers.
Your built-in PRE-amp/controller is probably doing all the controlling you need. By the way, your Denon 3805 is a pretty fine receiver & should produce all the "pumped up" volume you need unless attempting to power concerts to the entire neighborhood; in which case you will be hearing from the neighbors.
i wanted to know wats the difference between an amplifier and pre-amplifier.also if i want to pump up the volume of my a/v receiver will the pre amp do the trick and do i need seperate pre amps fer every channel??? my reveiver is denon 3805.