When you buy new headphones your brain is always used to the old ones and it always takes a week or so to adjust.Usually we always find a headphones tonality weird at first, even if its a super neutral one like the 560s.

And coming from the really bassy xm4s, that could be a weird process.

I would advise you against returning the hd560s... give them a couple of weeks of frequent listening to get to you.

I can actually tell you that the hd 560s have really linear bass and are the pair of headphones I own that have the most sub bass (disregarding iems). You will probably end up liking their bass and their overall superior linear fr and technicalities if you give them a chance.

And if you never get used tho their bass, then 70% of all audiophile headphones just got off your potential buy list....