Mine arrive tomorrow, friend already has his so I can confirm.  500 is "balance" mode, 550 is "turbo" mode.  I have heard that people were getting close to 50kh in the discord I am in, but my friend gets around 44-46kh in turbo mode and very quiet meaning the damn miner isn't even trying.  This miner should be able to do at least 600-650m but we need to figure out how to actually overclock to that.  Also, the inspect element trick does not seem to work and no firmware other than what it has to try so we gotta figure out another way unless we do actual editing of the cfg file.