Jkscherk
I did that last summer and compared my macmini(JRiver vs my sonos and it was clear to me that the mini sounded fuller.Both went through the same dac and electronics,same songs and same volume level.Also files were on external Lacie drive on the macmini,and NAS Western Digital My Book Live for Sonos.
I admit the Sonos has an excellent interface though,and the CR-200 controller is so easy and convenient to use.But the JRiver music player is no slouch either.I use a wireless apple keyboard and mouse for now on my macmini,viewing the playlists through a 23 inch display.
Best
George