Which would you buy: dCS Rossini non-Apex or dCS Bartok Apex?

I would not. I am not fond of the dCS sound. I appreciate it, understand why many would like it. It is very detailed and spatially accurate with very low noise floor. But it is too polite, with less nuanced bass and warmth. It misses the soul of the music to me.

So I can understand your comment in perspective, which DAC(s) do you prefer over dcs?

I own an Audio Research Reference CD9 SE. I have also had in my system a Berkeley Reference Alpha 3P, Accuphase DC 1000 and I hear that the Music Fidelity Nu Vista pretty good for the money.