The capacitor quality has more to do with reliability than sound quality... If anything it'd fail before you notice any degradation. There seems to be some confusion about the caps actually used too, something about OEM cards having different ones etc... The thread on the audio section had some posts about it.
The caps FILTER the sound. They have a significant effect on the card's sound quality. Read this thread:
http://forums.guru3d.com/showthread.php?t=254935
ALL Creative cards except for the Titanium HD and the ZX/ZXR use Jamicons. That's why so many of them have died in past. Also, My X-Fi Elite Pro clearly DID NOT sound as well as it did in 2006 in 2011. I could easily hear that it was sounding worse due to the aged caps till one day one of them just leaked. Card dead. Terrible.