...which means I have to analyze the gain for all my files...
There are specs that define what RG should do, but unfortunately there is no agreed on standard for how it's implemented. This is the method that MJs developers felt worked best in their application.
...reduce them to 83db so they are not louder than they are already.
Well, the purpose of Replay Gain is not to make files louder, it's to make a group of files the same loudness. If you achieve this goal by
raising the gain to match the loudest files, you also run the risk of introducing clipping. Also, as mentioned in another post, the movie industry was already using the 83dB target, so that's what was used in the original RG specs.
And, at least with MJ you're only saving the gain info to the tags (like Vorbisgain and Replay Gain for MPC) rather than permanently altering the files (like MP3gain) and possibly ruining them by accidentally choosing too high of a gain setting. If you want to play them at their original level you can just disable the RG DSP.
Rob