Re: OPPO BDP-83 Bluray player
The price difference isn't huge at $210 but it isn't small either. The primary difference is the better standard DVD upscaling and de-interlacing in the 83 which has the ABT video chip rather than the Mediatek basic upscaling. The difference would probably not be noticeable on a screen below 50".
The 83 also has better analog audio performance with its separate stereo analog out system (the 83SE is better for analog still and not by a little bit). Again if you do not need analog audio (for stereo SACDs and CDs), then this feature is not something you would need. If you are going to send all audio over HDMI, the improved analog audio performance would again be irrelevant.
Finally, with the latest firmware, the 83 can work with a DLNA server to allow streaming media (this is NOT streaming video downloads from Netflix or some other service) which allows you to send video from a media server or your computer through the 83 (taking advantage of its upscaling abilities where appropriate). The 80 so far does not have this last DLNA ability but it may possibly at some time.
The other differences that are in the 83's favor are build quality and extra features ones, such as the aluminum rather than plastic faceplate, heavier chassis, support for IR repeaters and the availability of an option RS-232 input for use with sophisticated control systems.