I really want to say try a used set of ProAc’s like the Tablet or any in that model rang over the years. possibly the Response 1sc, 1.5 if you can take a small floor model. Great imaging speaker huge width and depth and detailed but not in your face detailed more refined then most smaller speakers for the size and money. ProAc speakers are known for their musicality and imaging, they play nice with tubes only thing they may not do enough of is the hard edges you like but the newer you get the more refined they get.
you could also almost buy a new set for the same price as the LS50
of the current tablet 10. in either ported or none ported versions.
I started my Audiophile journey in the proac Line, still miss them to this day.