I have had both actually. I first had a Creative Audigy card. Then I went to X-fi. I liked it but the control panel wasn't to my style, and was able to sell it for the price I bought it for and the Xonar I heard was on sale. The difference was 0_0. Using FOOBAR and legit high quality songs. Plus, look at the caps and parts and OP amps and the circuitry, then tell what is better.
Note: If you have W7, there is no such thing as a "gaming sound card". The EAX support is gone. So all you're left with is a card.
Now if you look up comparisons, the Xonar beats the Titanium in terms of sound quality and other things. This whole EAX is such rubbish. Ignore it.
I can go on with the list.
Bottom line: Get the DX. If you need more info or anything let me know!