Harri
I personally find that a "spun" disc tends to sound more "live" than computer audio. I currently own a Weiss INT202 FireWire interface, a Wavelink HS and have used M2Tech async, Bel Canto uLink (synchronous) as well as built in USB ports of various DACs and own an EMM Labs XDS1, Ayon CD5S, Bel Canto DAC3.5VB MkII, previously Benchmark DAC1 and it seems to be true across many different platforms and implementation.
The Bel Canto in particular sounds very good with the matching CD2 as a transport.
So I suspect that what you are comparing isn't the difference in DAC per se, but a preference for the spun disc on the C5 vs computer audio on the QB9.
Computer audio has progressed at an incredibly fast pace in the last few years and it may be that it would overtake the spun disc in a few more generations of technology. Who knows?
A friend of mine swears by his Empirical Audio Offramp and it does seem a noticeable step up from my Wavelink HS.