If looking for another hp the Hifiman he1000se would give you a cross of the hd800 and utopia (i have never owned the hd800s to comment on that specifically).
Different to the utopias bit with as much precision as the utopias in its presentation and a wide soundstage and upper end a bit like the hd800.
Not as full a sound as the utopia. Tight bottom end.
Or empyreans. The detail will not be at the same level (or at least not as obviously apparent) but it will give you a fuller mids/lower end sound and kinda lush tone in that area. Different to what you already have. Probably worth brightening it a little with a silver cable and/or touch of eq at around 1khz
no problems driving either
btw the hekse sound great out of anything imho so can lug around the house straight out of, say, an iPhone or iPad and save the better listening session when sitting by the studio six with any of the above mentioned hp.
Not as sexy as a second tube amp though - i know