^ - I'm having the Creative X-Fi Titanium Card
Creative PCI Express Sound Blaster X-Fi Titanium Fatal1ty Professional Series Sound Card
I bought the z5500 and this sound card, when I had excess money in my hand. So I sought for the best. But if you ask me, I'd definitely recommend you not to buy a sound card.
I had a creative inspire 5.1 once. Switching from Inspire 5.1 -> z5500 (onboard) -> z5500 (optical) -> z5500 (cretive titanium) gave me an audio quality boost of
25->75->90->92. (Edit: 25->75->90->95, after listening once again - Inception DTS 1536 kbps)
Now think for yourself, do you really want to spend on that 10K/6K for getting that extra 2 point audio quality increase?
But, of course, the sound card gives you a lot of features, but i seldom use it. Check whether optical cable gives you 5.1 sound in gaming, if so, better stick with digital output. No need of buying the sound card.
P.S: Before replying this post, I tested once again just to make sure.
Music: Aaromale By Rahman (Vinnaithaandi Varuvaaya) - FLAC
Movie: Climax I (Dodging gunshot first time + Helicopter drive by trinity) and Climax II (Firefight in the basement) - DTS 1536 kbps