Fine, that you like your PM-1 with the RS250.
I’m using a Hifiman HE1000V2, a Beyerdynamic T1, an Oppo LCD-2 and LCD-XC, a Sennheiser HD800 and T5P1, a Focal Clear MG…
Also I’ve multiple headphone amps and so it’s easy to compare them with the heaphone out from the RS250.
For all my magnetostatic headphones, the Rose hasn’t enough power and it’s also not able to drive the HD800 or the T1.
Also it seems, that the output impedance isn’t low enough for headphones with lower impedance.
Not tested yet my Campfire Audio Solaris 2020 with the RS250, but also the Focal Clear MG doesn’t sounds very good with the RS250.
Now I’ve connected a Burson Conductor 3xp and an ifi Gryphon on the RS250 and both sounding with my headphones as expected (compared with the many other dedicated headphone amps).