Damn, I was always interested in the MDR-7520, but at the time I was researching on it, there were very little reviews. I currently am using the MDR-1R as my go-to headphones for portability, but I find it to be lacking in many areas. The treble isn't as detailed as I want it to be, the mids also lack resolution and the bass is too mid-bass centric and quite rolled off.
Do you think the 7520 could be a potential upgrade to my MDR-1R?
Yes, definitely an upgrade in all areas you mention. I listened to the MDR-1R over the weekend and it's nice but too tipped up on both ends for me. The 7520 sounds like a full size headphone, not a portable.