Yeah, I'm also interested in hearing some more opinions about this. Currently, I'm using the same OpAmp combo as OP.
There's quite a few posts burried deep within the The Xonar Essence STX Q/A, tweaking, impressions thread, and from what I've read it seems that the 2xLME49720NA / LM6172 seems to be the best / the most popular combination. While I'm quite happy with the sound, I still wonder if anyone's made a switch to a different combo that proved to be even better. Maybe I could be even happier? I would experiment with it myself if getting the OpAmps I'd need wasn't so damn expensive where I live. I think it'd be worth mentioning what kind of headphones (and external amp, if any) one uses with the card.
