I have been using Raspberry Pi+(Version 1) for years with Volumio 1.x and it has been great but since most of my tracks are FLAC, Gigabit can help.
I almost bought Odroid C2 which has built-in Gigabit network but for the price and purpose of my main usage, I settled with Raspberry Pi+ 3 with USB Gigabit Adapter.
I tried two(2) different USB Gigabit Adapter for Volumio 2.0, Linksys USB 3.0(https://amzn.com/B00LIW8TBG) and TRENDnet USB 3.0(https://amzn.com/B00FFJ0RKE).
The TRENDnet USB 3.0 Gigabit adapter works fine but it has a bit of issue with providing steady stream of the data so I hear “chirps” during play.
The Linksys USB 3.0 Gigabit adapter does not have that problem.
Here is what I had to do to Volumio 3.0 in order to recognize and use USB Gigabit adapter:
/etc/network/interfaces:
auto eth1
allow-hotplug eth1
iface eth1 inet dhcp