Funny you should ask! I will be comparing the D90 to the latest RME ADI2 DAC FS as soon as I get it from RME sometime next month. As far as the inferiority of the Anthem DAC, keep in mind that the new RME DAC replaced the AKM4490 with the AKM4493 which is arguably "inferior" to more expensive chips from AKM. Here's
RME angle in discussing the 4493/4497/4490 (posted 12 months ago!):
"Yes, the 4493 is a slightly improved version, but it is not fully compatible. The 4497/99 are forced replies to the ESS chips and their marketing efforts and success. But the 4497 did not cut the cake for various reasons. The new 4499 is much more promising due to its four channel architecture, and might get more popular than the 4497...in the long term, so far this chip is not yet available."
And here's
RME's explanation as to what is improved in the new DAC (nothing related to the 4493 apparently):
"Objectively there is no audible sound difference in music playback between old and new DAC. Think about it: nobody heard noise or distortion on the old unit. Frequency response, feature set and other tech specs are unchanged, so how can the new unit sound different? Technical improvements must not be immediately noticeable to still make sense. Like the added 2.5 dB headroom for the volume control (my favourite in daily use), the increased intersample peak headroom when using the unit at 0 dB volume setting (peace of mind for scared listeners), or the 2 dB lower noise at the (already noise free) IEM output (just because we can...)."
I chose the new RME because improved IEM noise floor and equalizer function (which the last one also had).