Looking At CD Players

I can comment on the Yamaha CD-S 2100 since you mentioned it specifically and not just because I own one...

It's a superb design and in addition to excellent sound quality offers a lot of flexibility. SACD, CD, USB DAC. The build quality is excellent. Its drive mechanism is something you'd expect to see in an Esoteric unit. Not a single piece of plastic in sight.

The only con i can come up with is toggling through the input selections is slower than expected. 

There are only a couple of pro reviews out there on the S2100, one from a new zealand magazine. Its pretty accurate and worth a search.

Not sure why you would want to replace your Oppo BD 105? 
I love my Oppo BD 105 and keeping it! I'm running balanced outs from the Oppo into my ARC LS15 Pre Amp But in the interst of me getting into Hi rez Streaming, and taking my music quality up a level, I just purchased the Exogal Comet DAC Plus and I'm going to add the Zen Mini MK III streamer that can also rip CD's to an enternal HD

I own both an Oppo 205 (stock) and a Cambridge 851C and the Cambridge is hands down better to my ears.

Because it uses a hybrid multibit/delta sigma, and for CD this is going to sound better than all delta sigma.

Even better again for CD is all R2R Multibit. as nothing does 16/44 24/96 DXD or CD conversion better than true R2R Multibit, latest discrete ones or the older no longer made chip converters like the PCM1704K ect ect

Cheers George

I own the 205 and a friend has the Mohican. The Mohican is mated with his Hegel Integrated. That sound is amazing. He uses focal Kanta 2s
and I listen to older Tannoy dual Concentrics with tube power.
I have brought the same cd over multiple times and marvel about 
how the different the two systems make the same music sound.
Not any sort of a scientific comparison but I would trade my Oppo plus $2k for his Mohikan.

I forgot about this CD-S2100 review which offers some comparisons with the Oppo 105 you currently own:https://hometheaterreview.com/yamaha-cd-s2100-cdsacd-player-reviewed/
Here's the Aussie review  (sorry kiwis) I mentioned earlier. It's in PDF format:
http://i.nextmedia.com.au/Assets/yamaha_cd-s2100_cd_player_review_test.pdf
I recently watched a Darko review on the Hegel unit. While some of the YouTube reviewers lack integrity, Darko is a pretty straight shooter in my opinion. The Hegel looks like it could also be a nice step up from the Oppo.

Since Oppo is no longer produced, it seems like a poor decision to spend a lot of money modding it. Like modded cars, you'll never see that money back at resale time as buyers won't have any idea if your mods are going to be to their liking. As suggested by another poster, you're probably better off using the Oppo as a transport and running it through a DAC of your choice.

Let us know how you make out.