Motherboard SDIF Output Or Soundcard

I would recommend an USB Interface and a USB isolator.  I use a Schiit Wyrd ($99) to isolate the USB signal from a noisy computer port and then a Gustard U12 ($160) to convert to spdif.  The Gustard has dual TXCO to minimize jitter and it sounds fantastic.  

gdnrbob:  Yes there is a significant difference.  The sound is tighter with a lower noise floor.  USB ports on computers are VERY noisy devices and the Wyrd repeater helps.  What I like about it is that it uses a linear power supply (the adapter is AC) and then has precision regulation inside the unit.  It worked so well for me that I ended up buying a second unit to be used at my office.  For $99 it does its job well.  Even high-end dacs can benefit from it.