New iMac, no more Optical out! Help with DAC, best bang for buck?

Hoping to at least match the sound quality that was coming from my Mac Pro to an older B&K 307 receiver via Optical cable out/in.  New iMacs do not have anything so USB is now the route. 
As you can imagine one can spend btween $20 and $1k+ for such a device. 

I had zero problems with my 2009 Mac Pro optical and the Mac's own DAC and my ears are pretty demanding. If I spend over $1k then I may as well get a Peach Tree et al. But right now I just want some kind of affordable medium to get my sound back while I research something for high-end and longer term.

Sound Blasters are between $50-$125 on Amazon. Anything cheaper that would make me happy? THX!!
PS - Also would an older Airport Xpress with AirTunes work for this? I'm seeing these things on FB Marketplace going for peanuts these days, especially since most don't know how to read the model # ;)
All you need is a 2nd generation Apple Airport Exppress or 3rd generation Apple TV. These are available used for $40 to $60. You can than stream your music wirelessly from your iMac to one of these devices and use their optical output to your recieiver. Your computer can than be in any room of your house. You can use an iPhone or iPad as a remote. Very simple and works flawlessly. I have been doing this for over 8 years on 3 different systems in different rooms and never had a failure or dropout. My wife even has her own system using her MacBook Pro.
I'm running USB from an old iMac into a Schiit Modi 2 Uber then into my line stage. I'm generally happy with it. I got it for $110 used.
The Dragonfly Black or Audioengine D3 should work. Connect to inputs om you receiver with a 3,5mm to RCA cable.
You could try the Behringer U control 202 about $30 on amazon. It can do more than you want but should work using your same cable. You can look it up on Macworld ’How to replace the missing digital - optical audio output on newer macs.’
So I did get a used APE and then spent another $10 on a converter plug tip for my optical cable.
It DOES kinda work, however the lag in sound actually will create a lag in the Mac's function to make sure it syncs! Pretty intelligent but useless if you are using it as an extension of your regular computer speakers. So any video clip or YT or anything like a game would be a slight lag even though my amp/Pre is 4' away from me. Will check out the D3 and Schiit and use Airtunes to replace the pretty much defunct Medialink for my PS3
HEY...another update - 

I have a Schiit Modi 2 available on a local listing $50, and the Behringer 202 on Amazon for $30 but one of the reviews or answers says 16-bit "is probably good for 320 MP3's" - that makes me hesitant because it's 2011 technology and I like to listen to the best 1400kbs WAV or AICC files if lossless rips - plus, Tidal streams in CD quality - that would be 1400.
I see a more recent Behringer for $40, the 22 model. Will this also provide Optical out to my receiver?
Are you saying you have a lag streaming music from your iMac to the Airport Express? I have never experienced a lag. Just wondering if that is what you meant.