So actually, you are asking which DAC is best for PC? As both an outboard DAC and sound card convert the digital into analog signals.
Not having heard the Links card, but owning the BC D3 as does the above poster, though with differeing electronics, I'd say the Bel is better just on GP. Not even counting the anciliary benefits the BC D3 affords one.
However.... would you go get the Links card if someone says it is better, not having tried it yourself?
Personally, I'm curious too about this facet of digital PC dbased audio. Primarily because USB DACs usually only allow for 16/44.1K input signals... and I've noted diffs in upsampling that signal to higher values. 24/96, 24/192.
Then also, the use of different media playuers will demonstrate better or lesser sound as well. Trust me on that bit.
Shortly, I'm going to add a 192 card and find out for myself.... which is ALWAYS our best path in determinging the answwer to a "What's best?" question. And because I'm hard to convince.