I just received my Asus Xonar DX in the mail to replace the SB X-Fi Titanium I received for Christmas- I gave up on dealing with the system freezes and multitude of bugs that it brought.
So far, I'm only getting bitperfect in Foobar with WASAPI set to S/PDIF. ASIO is NOT bitperfect for me on this card. I'll keep playing with it.
Edit: I guess this isn't really a problem. WASAPI is playing back not only 44.1KHz audio as expected but also 48KHz without complaints. The only thing that's lost is the ability to have other sounds mixed with bitperfect music like my X-Fi did on the rare occasion that it worked.