Long time lurker - first time poster (well, actually second - I made the cardinal sin of posting duplicate material with my initial post

) but this is my first question related to my adventures in audio.
My current (and first set-up

) contains:
1. Squeeze Box Duet
2. Yulong DAH1
3. Cambridge Audio 640a V2
...so I have three different components to adjust the volume.
My question: Aside from pure experimentation and the guidance of my own ears where should I start to find the best sound? I currently have the Duet´s volume at 100% and my amp is static while I adjust the preamp in the Yulong.
Thanks for taking the time to read this.