If you feel the need to spend money go ahead. But your DAC already has a circuit to convert from USB to I2S which is exactly what the Singxer does. In other words, it duplicates exactly what you already have. Unless you have reason to believe it will do that much better, and noticeably so, there's really no need.
Devices that can transmit the I2S AND eliminate the USB function entirely might be expected, theoretically, to improve SQ. Typically they have Ethernet input and I2S output. But that's not what a Singxer SU-2 does.