500 looks portable ,aka LunchBox... like a mini rack case. I could see the beneift in that I guess?
those old 6" half size desktop boxes like the DMP3, JoeMeek VC3, the RNC, the Grace M101 , Neve 5012 types, always seemed to be the "discount" version of the main 19" rack jobs, but it seemed more goodies were put into the 500 series. the transformers included etc,,,
I guess they share the power supply to save money.
time will tell. ive heard good things about the 500 series.