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 
128x128ghulamr
Don't waste money on a different DAC! The Benchmark is as fine a unit as you will ever need! It measures and sounds excellent! 
It does measure well but sounds digital and a bit forward. I am still trying to tweak it more - may replace the fuse with HiFi tuning supreme. Using Pangea AC-9 cord. Room for improvement adjusting the jumper settings and maybe replacing to better digital cable. Want to take the edge of higher frequency and make the music less fatigue and more warm. Maybe its the Kanexpro that’s adding jitter and noise - the source maybe the weakest link. Thoughts..
Take a look at the Bluesound Node 2i streamer. It should prove to be a good option for you and scales nicely when you add a better DAC to the mix. As to your DAC, I think you're on the right track, IIRC the DAC1 was known to be somewhat bright and "digital" sounding (I never heard one). 
If it works well, the Bluesound Node 2i will fill all your needs.  I have the Node2, which has an ok DAC , but the 2i is supposed to have a better DAC still.  My problem with Bluesound has been reliability issues, most of which stem from problems after one of their frequent updates.  Their customer service used to be very good but has really deteriorated recently.
btw, have you tried using the Network part of your Oppo to control your NAS?  That’s what I’ve been doing with my Bluesound dead in the water.  I also have been using my MAC Air with Audirvana +.and this sounds truly excellent.  
@mahler123 .. surprised to read of Bluesound's customer service decline. That's really a shame. I've had the Node 2 for almost 3 years and it's worked without issue for all that time. (I have 2 Pulse Flex units as well.) That being said, I recently moved on to a Sonore microRendu and the Node 2 is now in my work space streaming mostly internet radio streams and occasionally Spotify. BTW, I've read the DAC is the same in the 2i and the sound quality improvements have everything to do with an upgraded wifi module and some circuit board changes. Haven't heard it myself though.