Two DAC in One System Sound the Same?

The DAC chip is only 1 aspect of the sound you will hear. The same DAC in 2 different DACs could sound very different depending on the output stage and other aspects of the DAC (plus other components). I also think most DACs in the under $2k level are not going to sound too different, unless you get a Schiit DAC.

Toslink does not have to be always bad. I believe if you keep the cable short and in good shape the sound should be very good.

You also have to consider the resolution of your gear. I have not heard your gear but if the amp, speakers, cables et al are not up to it you are not going to hear differences that easily.

Lastly, your hearing has to also be considered. I recently had some vertigo that I was dealing with. I had my hearing tested and found that 1 ear was hearing perfectly, the other was hearing slightly less. I think that was due to the vertigo which I got from a drug I took. 

BTW - the Shanling SACD transport is on my list to get.

I also think most DACs in the under $2k level are not going to sound too different, unless you get a Schiit DAC.

I agree with this. These DAC chips are mass produced and their implementations in these units will be very standard / basic. The good news is the math & engineering behind these DAC chips has been developed for a very long time now and does its job VERY well. You want a different sound, you need a more exotic / bespoke design - which either can’t exist at this price point, or just slaps on a cheap tube buffer (cheesy), or is a plain bad implementation. At 2K (used) a Schiit Yggdrasil would do the trick if your system’s up to task. It’s fantastic. If you're going to ask "what about a Gungnir" (model below Yggy), I wouldn't. I've owned both and the Yggy creams the Gumby (Gungnir multibit).

Also, I’ve rolled many of each component type in my systems for a long time and in general DACs have less range & magnitude of different sound versus the other major components imo. From what you describe your result is not unexpected to me. 

I found with much more different DACs, a Topping D50III chip vs. a Holoaudio May L2 ladder, the differences were minute. I am not surprised that you find zero difference in two chip DACs.

Sometimes the differences are very subtle, and can take some time to pick up on.  Suggest you get extremely familiar with one for a couple of weeks, then switch and get extremely familiar with the other.  Switch back after a couple of weeks, and repeat....if you still don't notice a difference, either they're too similar to detect or something else in the system is masking the small difference.