Your headphones are similar to what I have, Rega Ear Mk1 with AKG 701's and Beyer Dynamics DT880's, small differences in the sound presentation, but not massive.
Did the upgrade path, the Naim Headline with Napsc, apart from going louder not much difference to the Rega.
Then up to the Quad PA One with a pair of Sennheiser HD800's.
Result back to the Rega with AKG 701's and Beyer's, the differences are pretty small for the amout of money involved when upgrading.
Headphones are a very personal thing, it is the fit to your ears and head that make the difference over long listening sessions.
As has been said easy to play too loud and that will cost you your hearing in the long run, you might not think it is loud but headphones can be deceiving, play them then ask someone to listen at the same volume, you might be surprised how often they will say, way to loud.
The only headphones I might upgrade to would be a pair of Stax, however having heard some I think I would find them fatiguing over a long period of listening as to my ears they were quite bright and strident.
That is my my feelings on headphones, many will disagree, each to their own, also a quick listen is a not the way to audition, you need to use them over a couple of nights to get the feeling of how they fit to your ears and head and how they sound.