Since 2013 I'm using and working with the Raspberry Pi and contributing this or that to the community.
The Raspberry PI family is by far the most successful single-board-computer (SBC).
Even if its base hardware can't be considered top notch, it can very well serve the purpose
of becoming a serious audio transport.
What makes a device like the RPI a success story is its wide market presence,
great and innovative SW (community) support and OEMs flooding the market with
all kind of (quality) gadgets.
Many other SBC companies failed to succeed (beyond becoming a niche product), because they were not able comply to these factors - even providing a potentially much better HW base wouldn't help.
Building HW is a one-off effort. Without SW these devices are worth nothing.
Providing, evolving and maintaining SW is a continuous process over a long period in time.
That's what many manufactures underestimate! And that's why they usually fail.
Taking a rather mediocre device (HW) like an RPI and make it a high quality audio transport.
With this article I'd like to give a little guidance to get you going.