I think perhaps the most important aspect for sound cards, in relation to gaming, is the implementation of the 3D sound drivers. I have had terrible problems with sound cards on my new computer, and for that reason have tried a bunch of different ones, including the onboard sound, Creative SB16, Turtle Beach Santa Cruz, and Creative SB Live 5.1. Each had quite different implementation of 3D sound, things like attenuation of distant outside sounds, doppler shift, etc. For example, the Santa Cruz had a bug in the 3D drivers (perhaps since fixed) that caused all outside sound to be virtually inaudible- ie a Panzer could drive right up next to you and you wouldn't hear it. Conversely, the SB Live 5.1 had the best handling of external sound, with very realistic doppler, proper attenuation, and even very realistic filtering of distant sounds (ie that distant muffled character). On the other hand, the Creative installation software totally munged my system on many attempts (including nuking my Registry forcing use of a backup Regsitry that was out of date).
My experience was with Win98SE on an Intel 865 MB with a 2.8C GHz P4. Your mileage will undoubtely vary and you shouldn't make judgements based on one person's experience.
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