Got one of the AK4497EQ DAC boards from Ebay. Using the new XMOS U208 based USB to I2S Bus board I already have to drive the PCM and DSD sides for use with my headphone rig. The USB driver is on a link from the Ebay page.
The first trial is checking DAC DC offset and if very low bypass the 2 - 100uF AC coupling caps at the output of the DAC chip feeding the filters. Will probably use a 49720 dual opamp for the output filter and drive stage if the offset is low.
The DAC board I have uses balanced outputs, so easy to try with a balanced drive amp to the headphones.