Your Stellar Gain Cell DAC will play up to DSD 128 (DoP) through USB and up to DSD 128 direct through a compatible I2S device, the only compatible I2S devices I know of play DSD 64. Perhaps the MATRIX USB to I2S does support DSD 128.
Works great from my iMac with BitPerfect and DSD Master converted hybrid ALAC / DSD 128 files in Apple Music, but there are plenty codecs fo PC as well. I use the USB connection.