RE: replacing H390 with 590.
You don’t mention a DAC so I assume you’re using the 390’s on-board DAC, which is somewhat on the lean side.
I’m not familiar with your speakers. I also own an H390 and Jay’s CDT2MKII. Both my Silverline monitors and Aqua La Voce DAC are on the warm side and I had to swap out ICs and footers in order to tame what was, for me, too forward of a sound, in conjunction with the 390 and Jay’s.
Be aware that the H590 is both more resolving and more neutral than the 390. You might consider purchasing a 590 from a seller that offers a return policy, such as Listen Up! as moving up the Hegel line might prove "too much of a good thing", depending upon your taste.
Just my 2 cents...
BTW, I'd be very curious to know what you think of the QStab.