Hi, bomd,
The Oppo 103 is not the same as the Oppo 105 when comparing sound quality; the 105 is a better player. I have a 103 and it's fine as a CD transport but the sound quality of its internal DAC is not as good compared to the internal DAC of a Rega Apollo or the Node 2, which I also own. The Node 2/2i has a better interface than the Oppo 103 if you plan on using an external USB drive for playback and if you end up with a NAS drive for file storage (which I use) the Node 2/2i works really well.
If you need a multi-player and have a limited budget then a used Oppo 105 is probably an OK choice. Any time you buy a used mechanical device it will be an unknown risk and whether Oppo will continue to service its discontinued models is even less certain. But if you're really looking for a digital player/streamer/bridge than the Node 2i is an excellent choice for $500. If you can find a new Node 2 for less, all the better. As others have pointed out, the sound quality of the Node 2/2i can be improved with an external DAC (that's what I do) but the internal DAC is actually quite good.
Ask a dozen people for advice and you'll get a dozen different suggestions. '-)
Regards,
Tom