Guily, the one you linked to is the OPA627 by Burr Brown. That's actually the one I was talking about, the real ones are about $20-$30 per chip and you need 2 for stereo. I would guess that for 7.1, you would need 7 of them which would be approaching $200. For that price, you can buy a discrete DAC that would beat the whole sound card.
Also, there may be good opamps and caps on the card but it still comprimises with the DAC since the DAC has to output multichannel, they can't use a good DAC chip setup for the best dynamic range. With current tech, it's pretty easy to get 128 or 129 DB in SNR and dynamic range yet your card is rated 98-115 DB depending on output.
For a 1FPS gain, spend 20 seconds and overclock your CPU/Memory/GPU 5-10% and you'll see more gain than you would with the sound card. Creative is getting left in the dust, all of their hardware features can be done faster and better in software with OpenAL. Other companies like Rapture are leading that front.
I used to have a Creative X-Fi XtremeGamer that I had modified with better opamps and capacitors along with a few other mods that cleaned up the signal path. It was fine and in some older games it was nice to have the extra EAX effects. But, looking back, I don't regret getting rid of it. Modern games have great software-based sound outputs that make you feel completely immersed. IMO what matters most is the speakers/headphones you use, without good ones, it doesn't matter if you use motherboard sound or have a $500 dedicated DAC, it's still going to sound like shit