I wouldn't be too worked about them being fake, although it is obviously a possibility. My computer had significant hissing and I purchased an odac/o2 combo. I haven't heard the modi bUT it seems to be very good and often compared with the 02. My deciding factor is I travel and the o2 was compact. Honestly I think the 598s sound just fine out of a phone so I imagine any neutral amp Dac should do great. As far as burn in you will adjust to the 598s presentation but I personally don't think the headphone changes. After a week or two of the 598 I would be curious to hear your impression of the dt990 if you still have them.