You do not need the 105. The first thing you'll notice with the 103 or 103D is that they are quite a bit faster than the 83 you are using now.
You'll also gain some Internet services that you might enjoy such as VUDU or Netflix.
There are more subtle improvements in audio and video processing capabilities that you may or may not notice. If you do ever get into playing media files instead of shiny discs you'll find the new OPPO players far FAR more capable than the 83.
Oh, also the new players have no fan. Some folks get annoyed by fan noise from the 83.