Budget Music Streamer

I've been trying to get my head around best sound out of a budget streamer. All my CD collection is now in my portable 2TB hard drive as FLAC files and I also have subscription to Apple Music (large playlist). Currently using Apple TV and Airport Express (airplay limiting to 16 bit/44.1kHz) and Apple TV streaming at 48kHz. I have a revealing system and know I can get better sonics by upgrading my digital source. Unfortunately I have been blessed with a good ear for music.  

There are quite a few options out there, each having it's limitations, specially the ability to play Apple music directly from iTunes using a remote without limiting the sampling rate. Do I consider a Mac Mini or build my Raspberry Pi source? Will I get a spdif connection (preference) out of the two? Is there remote control capability to view playlist (I don't intend to hook up a monitor). Or is there a better solution out there for both listening to FLAC files on hard drive and streaming Apple Music? I plan on selling my OPPO player - no use to me, to fund a better DAC (schiit Yggdrasil or BorderPatrol) - hence the digital source is on a budget. Experts chime in..

Simaudio W5 poweramp
Von Schweikerts VR4 
OPPO 105 
Apple TV (using Kanexpro HDMI de-embedder to extract audio - coax in DAC)
Airport Express (optical in DAC)
Benchmark DAC1 (no USB) - used as preamp
Marantz AV7701 preamp
Morrow Audio interconnects