We all have to start somewhere
. Some of the confusion arises because of the terminology..
A basic hifi audio system is: Source - Preamp - Power Amplifier - Speakers
A Receiver like your Sony incorporates a source (radio tuner), preamp and power amplifier. Other sources can added via the inputs.
The source must be a line level source, such as CD/DVD etc for these inputs.
A turntable system, that is the cartridge, only outputs a very small signal & this has to be 'pre-amplified' to reach line level for input into a line level preamp. This is what your Pluto does & what the Reduction/Eros do as well.
These are Phono Preamps or Phono Stages (not be confused with Line Level Preamps). Their output is then fed to the line level Preamp which then drives the Power Amplifier.
The Crack Headphone Amp needs a line level input. Your Pluto or other Phono Stage is still needed to drive the Crack amp.
A Reduction or Eros would replace the Pluto phono stage only. You still a line level preamp & a power amp (your Sony Receiver) to drive speakers.