n80 - if you want to apply mods to your Oppo 105D, it can sound better.
I own both an Oppo 105, and an Oppo 205 which have been modified by Ric Schultz at EVS.
tweak1 mentioned power supply upgrade. That is what Ric does for the Oppo, and it makes a difference. My unit also included a hand-built analog output stage.