The following I can attest to:
Out of the three Asus cards, the Xonar DGX is definitely the best one. It supports 7.1, while the others only support 5.1. The definition is also the best out of them.
The other ones are more geared toward gamers. The DX is more marketed to listeners who care more about clarity and definition.
The following I might need someone to piggyback on:
I'm more savvy to Asus cards, and I haven't tried Creative cards, but from what I understand, the Recon3D is actually worse, feature-wise, and quality-wise, to some on-board audio. I know for sure it only supports 5.1. By the sound of it, the Titanium is less than mind-blowing as well. I can't attest with much authority to the accuracy and integrity of that however.
I can only imagine that Asus is going to give you very good performance. They make the Essence STX, sometimes crowned one of the best cards you can get for anywhere remotely near it's Amazon price of $166 (as of Jan 4th). They make very trustworthy stuff, and people like me who are into awesome computer guts love them.
Again, I don't know much about Creative parts, so we may need someone to testify for them.
Either way, good luck, and enjoy whatever you decide on!
Edited by ninjapenguin120 - 1/4/14 at 12:26pm