Digital Advice

In your shoes with your budget I think you would be best off with a stand alone streamer with it's own built in DAC. Something like a Bluesound Node would fit right into your budget. Its user interface is both robust and intuitive, and supports a wide variety of streaming sources including Amazon HD. It would also provide you with a nice upgrade path should you choose to add a stand alone DAC down the road. Just my 2 cents. The Wiim products would also be worthy of consideration at a somewhat lower price point. For many of us products like these were the gateway to streaming.

I have a WiiM Ultra streamer/DAC and think it is fantastic for the money, which is well under your budget cap.  And you can buy it on Amazon which offers free returns if it doesn't float your boat.  For me, it falls in the "there is no reason not to try" catagory.

This Bluesound Vault will let you stream and you can also load all your CDs into it so you can have all your music from one source, and I believe it also works with Amazon Music. 

https://www.usaudiomart.com/details/650171585-bluesound-vault-2-streaming-music-player-with-2tb-drive-cd-ripper/

The WiiM Ultra is a great streamer via USB output. Using the Ultra with the onboard DAC was not my cup of tea. 
 

Perhaps the WiiM’s onboard DAC will be to your liking…..

The WiiM works with the vast majority of streaming platforms out there. I can personally vouch for the Plex and internet radio options working flawlessly. 

+1 for the Bluesound options.  I have the Node N130 and the Wiim Pro Plus.  The sound is better to me on the Node and the BluOs app works great streaming Qobuz and other streaming services including Amazon.  

@mybuddy

How have you ripped CDs to the Mac? If you use an Apple Optical device as the ripper, it can also be used to play CDs if it’s attached to the Mac. If you then add a Wiim streamer or Bluesound Node you are under budget.

Personally I would check out a CD player from NAD or a CD transport from the likes of Cambridge Audio . I would continue to use the computer attached to a DAC as your streamer. Dedicated streamers are just networking computers that are made to look and operate like audio components. They usually have better DACs than PCs have but you said you already own a DAC.  If you add a program such as Audirvana to the Mac then it works more like a streamer and less like a PC playing music and may potentially increase the audio quality

DAC & Mac = 0

Streamer DAC = 4 votes

A repurposed Mac allows me to spend the entire budget on a DAC. This should result in a better DAC. Also the Mac is already setup for streaming, and most of the CDs I own are on the hard drive. Surprised to see zero votes for this option. Why?

Our posts must have crossed.

There are posters here that will routinely dismiss CDs and tell any one inquiring about a new CDP to just stream.  They aren’t right or wrong, it’s just a preference.

Also the Mac is already setup for streaming, and most of the CDs I own are on the hard drive. Surprised to see zero votes for this option. Why?

Because your Mac is very noisy and a poor source for streaming, and even a budget streamer will sound much better.  The Vault I recommended above is in your price range and will do everything you’re looking for (including playing your CDs) and will sound much better than your Mac. 

Here’s a Schiit Bifrost DAC for $300. 
And the Audiolab 6000CDT CD Transport for $335

Use your Mac to stream to Schiit via USB. This will beat WiiM and Bluesound. 

New Vaults are over his budget. Personally I would stay away from a used Vaults. I don’t know what refurbished means, except they scrubbed the hard drive. My Vault started failing after about 3 years, right when the warranty was up. I think he is safer going with a Wiim and a transport, but adding a program like Audirvana greatly improves using a PC as a streamer, because it turns off some other parts of the PC that contribute to the noise. It probably costs the same as a Wiim

Moving away from computer streaming (MacBook/Audirvana) to a dedicated streamer (Aurender) produced significant improvement in all areas of SQ but most notably, the removal of fatiguing “digital glare”.  I recommend you make the move to a server/streamer.  Join a streaming service like Qobuz and they will have almost all the albums in your CD collection at your fingertips with SQ better than CD.  Burn any album in your collection not on Qobuz and your collection is complete and conveniently available.  If you can up your budget to $850-900 you can get a preowned Aurender N100H offering much better SQ than any Bluesound Node/Valt model.  If not, IFI has models in your budget liked by the press as an alternative to Bluesound.  

I would recommend Node - my rationale is it’s a streamer/DAC. You could connect your Mac to it and I found streaming to be a lot more convenient that sifting through my computer for files. 
 

I also prefer streaming DAC for simplicity. 

Check out the BlueSound Node N130 or newer. It streams Amazon and does great things for little money. New or used.

All the best.

Use your Mac to stream to Schiit via USB. This will beat WiiM and Bluesound. 

I'm not sure. I had been streaming from my Mac to a DAC for a long time before switching to dedicated streamers. I would suggest streaming from a Wiim to a good DAC instead. The weak link in both the Wiim Pro+ and Ultra is their internal DAC, but the RC and PEQ (with a good mic and proper setup) compensate for it, making them almost indispensable yet very affordable hi-fi gear.

The Blusound node can be bought for a couple hundred on the used market. The app is the best. I don't think there is a better low cost solution. I don't know if $600 elevates you much. 

Without going overboard - audphile1 has a solid suggestion. You might consider a new Schiit Miodi instead of the used Bifrost. It has a nice USB implementation that will isolate the DAC frrom your Mac.

https://www.schiit.com/products/modi-plus

With the budget you have, what I would do is drop the $600 on a used DAC and serviceable USB cable for the repurposed MAC.  Right now, that would be the biggest bang for your buck and give you a better upgrade path for the future.  And if you don't want to rip all your cd's to the MAC, and assuming the Denon 2900's problems are transport/laser based, then find a cheap, used CD player with coax/spdif output and connect it to the new DAC.  Then save up some money to add a dedicated streamer later.

• The Schiit Bifrost is a good, solid option for the DAC.  Make sure you stay with the Bifrost 2 or Bifrost 64/2.  There are other DAC's within your budget as well.  Just do your research first.
• +1 mahler123....Stay away from the older Bluesound Vaults.  The DAC's are old and they already have too many years on them.
• The newer Bluesound Node's are solid and you can pick up a used N130 for about $300 (or even a brand new Node Nano at $300).  Copy your CD rips to a USB drive and plug that into the Bluesound. You can then feed that into the better "new to you" DAC.

my 2 cents...

 DAC & Mac = 5

 Streamer DAC = 8 votes

After reading the many great advice my thought is I need to decide if this is an end game purchase or a start of a journey. An end game purchase requires 2-3x the budget I have now. Even those who suggested a streamer DAC at the $600 budget hinted at adding a separate DAC as an upgrade path.

One thing I learned here in selecting a streamer is to pick one with a good app. I admit I have to be educated here. I have only used the Amazon app to stream music & Apple Music to play burned CDs.