Resisted the urge to buy the Arya's and got some HD650 instead. I'm not very impressed with Sennheiser as a company recently but the 650s are great, a clear improvement on my HD555s and PC38x.
I haven't yet ordered an amp, but was suprised how well the USB C Apple dongle drives them on a PC. Based on what I read before I assumed i'd be having to nearly max the volume but at 40% they are loud enough (it's the US apple dongle with higher output than the EU version).
If the HD650 is anything like my HD660s, it will sound better with better amplification. My HD660S sounds pretty great when using my Focal Arche DAC/AMP that I bought for my Focal TOTLs.