Just for the record and future references, my uncapped WM1AM2 drives the new Sennheiser HD660S2 really well via BAL 4.4.
Having the Cayin RU6 (which I prefer over the N6ii x R01) and Schiit Modi Multibit, I can wholeheartedly agree with
@Sonywalkmanuser.
Sony DAPs have this analogue musicality many seek in R-2R DACs — with perhaps added advantages.
I originally considered a DAC/Amp combo (looking at the Jotunheim 2 with the MultiBit upgrade though they don't offer it with NOS like they do the new MultiBit 2) but listening to the WM1AM2 x Sennheiser HD660S2, it's going to be tough to justify the money aside having some nice Schiit with added power on my desk (which might be enough of a justification for many of us here
).