Most of the times brain will adjust it's base to a louder volume. So do this trick - start at an incredibly lower volume, increase volume in smaller increments until you manage to hear the song clearly and not any more. After sometime, reduce it by a notch and see if you can cope with that. Hopefully, that should make you get adjusted to the lower volume levels sooner.
A fellow head-fier remarked that "This hobby is a curse". No less for me too.
I'd suggest you slow down a little since you are already satisfied with RE-252. Make a wise investment that will be different from 252. Read up more on the following: TF10, IE8, Monster Miles Davis, MTPG, DDM, SM3. I'd still prefer TF10 (used) or DDM for you as others are costlier.