Converting from USB to SPDIF to I2S (computer to digital coax to DAC chip) is not optimal versus a well executed USB DAC which will convert from USB to I2S in one step. In general, the more you convert, the less good it's going to be.
It might turn out that you're quite happy in spite of the extra conversion step, which I think would be terrific because only your ears know.
If you do decide on a USB DAC in the future, amongst the many USB DACs out there, some that I would personally consider are:
Wavelength Cosecant
Red Wine Audio Isabellina
Audio Sector / Audio Zone
Wavelength Brick
UltraFi iRoc
I have either owned or auditioned all of these DACs, presently own the Isabellina and think it is fantastic.