A DAC for the Oppo 105

I haven't played discs a lot lately. I am and have always been a vinyl-dominate listener, and really got a CD player for the vinyl desert that began in the late 80's and really only abated in the 2010's. I found plenty of vinyl in those years, but these days, it pretty much automatic that there will be a vinyl release of almost all of the albums in which I am interested. 

So, because I am a music lover, and format is less important than the music, I did manage to get a pretty big CD collection - counting box sets, I am probably around 1500. I have burned maybe 400-500 of them onto a server, and that works great (I stream Qobuz, too and that is a great place to try out new things. Wonderful!) The idea that i would ever rip all of my CD collection into this server is a fantasy - I really doubt I will do this. So...

When I play a disc directly from the Oppo, I find myself distracted by elements of the sound that I don't care for - it can be a bit thin, unsaturated, a little fatiguing. When I play that same recording through the ripped file that goes from my Small Green Computer server, to the Sonore Optical Rendu, to my Ayre QB-9 Twenty DAC, it is much more as I like it. I assume most of this is because I prefer the Ayre DAC to the DAC built into the Oppo. Sadly, the Ayre DAC is USB only, and I can't take the Oppo digits and send them to the Ayre.

But since I am a realist, and will not rip my full CD collection, I am wondering if there is a relatively inexpensive DAC that I could use to improve the Oppo. That machine is getting old and DAC technology seems to be the end of the digital chain that improves the most, the most often. 

Any suggestions for an affordable upgrade to the DAC built into the Oppo?

Thanks,

David