Very newbie question: how do I tell if minimstreamer is runnng?

[simoncn]

The other factor that could come into play when you do the comparison is the "weakest link" effect. The audio signal passes through a number of stages on the way through your setup:

1) RPi1 receives HLS from your router and decodes it to AAC
2) RPi1 sends AAC over your network to RPi2
3) RPi2 converts AAC to LPCM
4) RPi2 transmits LPCM over HDMI to Arcam
5) Arcam converts LPCM to analogue audio
6) The analogue audio is amplified and played though your speakers

One of these stages is the weakest link in terms of sound quality and slight improvements in other stages might not make a noticeable difference to what you hear.