Thank you for caring to provide the links to the datasheets. But it seems that you erroneously picked the "28" instead of the mentioned "38". The correct link should be this one:
And the answer you quoted was about "what DACs were in the AVM70 and MRX 1140". Unfortunately, this does not tell us anything specific about the AVM 90.
FWIW, on facebook I found an answer that seems to come from Anthem:
"The AVM90 will be shipping with 32-bit/768kHz ESS DAC's(ES9038PRO)."
You can look it up under "/anthemav/photos/a.260678276657/10158858349741658/".
Too bad we have to guess, due to the conflicting sources such as in this case, facebook vs the Anthem technical advisor's response. If it is the 9038Pro, then I think Anthem can claim they have the best DAC IC for AV preamp/processors regardless of price! Even if they only use the 9038Q2M, it is still hard to beat, I can only think of the D+M's ES9018K2M that apparently the Denon AVR-A1H and the corresponding Marantz AVP will have, that have comparable specs.