X5 sounds good with SE5, in my memory, quite akin to 901 but not as good...but I did not like the shape and UI. Felt cheap to me.
For the cards, iem is to be avoided, sounded bad with SE5 to my ears, with sort of sibilant raspy mids. Balanced is good and discrete is more neutral. Never tried Minibox.
Never listened to DX9O.