Apple MacMini replacement or.....

I cannot find this question answered specifically in the archives. I have an aging Apple MacMini and I can no longer upgrade the OS and therefore cannot upgrade my Audirvana. This MM will not play the Masters Tidal or hi-Rez Qobuz. I have two USB storage drives, 500GB each in a Raid 1 which output to the MacMini. USB out of the MM to an Oppo Sonica DAC. I rarely play hi-Rez since I only have a few. It works flawlessly otherwise and streams to several Apple TVs throughout the house. I use iTunes with Bitperfect or Audirvana for playback. All the tunes load to RAM cache before playback to avoid Accessing the hard drive. Controlled by my iPad or iPhone.
I can replace the MM with a new one for $799. 128 GB SSD and 8 GB of RAM. Everything stays the same except I can upgrade all the software and have an SSD and stream from several classical streams that I like. The dilemma is this: Is this the best way to use my existing library of ALAC ripped CDs, keep music through the house, use my iPhone or iPad for controlling the music and have Apple reliability or is there a better way today? Or to put it another way, how much more do I have to spend to retain this functionality and have even better sound?
The rest of the system: 17 x 20 foot room with treated walls and carpeted floor, Modwright SWL 9.0 SE, Wyred4sound SX-500 monos and Von Schweikert VR-4JR speakers. Thank you.
Currently setting up a Mac Mini late 2014, 8 Gb RAM, 1 Gb HD,(almost new) as a dedicated music server which I found on Ebay for $305. This model will run the latest Mac OS & thus the latest Audirvana. I used the free SW "Mactracker" to find this model as it was recommended as the inexpensive alternative to a new Mac Mini. Mactracker lists the current price/value & has a link to the units available on Ebay. This model can be upgraded with an SSD if you're up for DIY and there are quite a few in various configurations available on Ebay. If you're happy with your setup this would be an inexpensive, easy way to go.I can't speak to the many alternatives, I'll leave that to the more knowledgeable people on the Forum.
@pushpull thank you. I’ll look it up. TG 
How about a Bluesound Node2i for $499?

It will do everything you want to do, play your library, use your phone as controller etc.
It is designed to be a music server.
It will play MQA and stream music via Tidal, Spotify, etc, etc thus giving you a much bigger library of new music and titles you don’t have.
It fits within your budget and has a good, up to date DAC.
The software can be updated, should last longer than a MM before it will be non-useable.
It should sound better than the MM.
You can upgrade the DAC later, thus improving the sound with time.

It will not function as a computer, cannot do all those things.
You will not be able to load different media serving software. The BluOS is what it uses.
It takes a little time to get used to as opposed to your familiar MM.

@2psyop perfect response to my question. Very much appreciated. I will investigate. TG 
you lose the computer you lose Audirvana... I really dig Audirvana.
Thank you. I understand. Sometimes I like it and sometimes I don’t. In my system sometimes Bitperfect seems clearer and cleaner. Very system and recording dependent. That becomes one of the questions concerning Bluesound Node. Much appreciate the responses so far. TG 
I think a Mac Mini is your best choice. I have been streaming my lossless ripped CDs from an iMac or MacBook Pro to an Apple TV or an Airport Express in 4 different rooms for over 8 years. Recently, I decided to set up a stand alone music server using a Mac Mini. I purchased a late 2014 Mini with 8 GB Ram and a 500 GB HD on eBay for $320. Setup was a breeze and it is performing flawlessly. 

I doubt a Node2i will sound better. We tried a Node2 a while back and with its internal DAC, it did not sound as good as an iMac, MacBook Pro, MacBook Air, or Mac Mini streaming to an Apple TV or Airport Express with our DACs. We could not tell a difference when we tried the Node2 using our external DACs. It certainly did not sound better. So the internal DAC may be the weak point in the Node2. 
Again, a perfect response to my question. So often a post gets derailed by promoters and sellers, or just argumentative people. Much appreciated. My only remaining question is how long a 2014 MM will last until I can’t update the OS?  Maybe by that time things are so different it won’t matter. I like plenty of RAM so I never access the HD during playback. And I have liked Audirvana and most people like the new version even more. Since I’m not going for the $10,000 set up with NAS, custom renderer, etc., I might just stay with Apple. I appreciate the responses so far. TG