I have the k371 and pretty large ears. My ears lightly touch the back of the headphone. The size of the ear cup is a bit smaller than I would like so it also feels a bit cramped but its not to bad. Brainwavz oval fit pretty well and will improve comfort but that will send you over your budget
With my Xbox one X I don’t need an amp. It moves pretty well my dt990 without one. Not perfect but works…
If anyone has a pair of mh751 or mh752 could you please measure how deep the drivers are from the ear pads please, I’ve been searching everywhere for this information but can’t seem to find it.