You get an extra deep bass layer due to some reverb things happening in the jumbopads, and that enormous airy soundstage (not the precisest in respect of placement of instruments though). Both leads to an extended genre bandwidth, they even do ambient and classical then. IMO a "plays everything" creature of the DT531 sort.
In respect of mids and treble, it's up to you. Without additional felt and all distancer drills open, you get a team treble can (CD3000 or DT931 sort), but you can mellow it stepwise down. I actually have a "medium stage of extension", and already then, my DT880 is much shriller.
You loose, say, a third of the stock oh-yeah-oh-babe Grado genes, but these parts get exchanged against a more audiophile presentation of the AKG K*01 sort. Not a bad swap IMO.