What I am trying to ask is this: even if the DC bias wouldn't hurt the input of the soundcard, would the divider be a reasonable solution? I'm thinking now that just a series cap would be easier.
[Edit: argh. That is not what I'm trying to ask. What I meant was: forget the soundcard. Assume the device we're outputting to has no AC coupling, or that I don't know whether it does. Would the divider be a suitable solution, or would the series cap be sufficient?)