Not all 24/96 audio is the same. There are a few things to consider.
Take for example the Sounb Blaster cards. On paper they have the highest recording rate for non-pro cards (and even many procards. However, they are considered lowend in the home recording studio. The biggest problem with Creative products is the poor driver support. So, drivers can definately effect the sound. The hard ware may (or may not be superior, but if it can't communicate well, the the over all effect is lessened. Currently, there stuff in on the edge of the consumer market, which can still provide a very good product.
ADC and DAC can be a weak point, if the converters are built poorly, cheaply, then there can be added noise, etc.... Converters have come a long way, but many small vendor may still use sub-par parts.
Some cards use system resources to help process these sounds. This could lead to strange noises and skippig/popping when the CPU usage reaches 100% (M-Audio, etc...) Some do this better than others. Some cards do most/all processing on board. This becomes more important when you play CPU intensive games.
Sound could even come down to the quality of the connectors. Not to mention speakers. Theoretically, they have the same max specs (or close), but real world expectations show that parts rarely meet their theoritical expectations.
96KHz & 192KHz sounds have been debated a lot. Many have come to the conclusion that the perceived difference is a result of the placebo effect (I know it's better, I spent more, it has to be better, there, you hear that, much better...) I won't say that no person can hear any difference, but it is unlikely.
However, there is a benifit to 192KHz, it gives you a much greater control of the final product (which would probably be converted one to many times before the final product. In this case it's like a director taking several shots of the same sceen for furture editting.
If you listen to music as the main point of your system, a card with a 96KHz output should be fine (as long as it is a good card Soundstorm, Audigy(2), etc...). Do some research, some 24bit/96KHz cards are junk, just like some GFti4600 cards were junk. The technology is the same, the GPU is the same, and yet different manufactures make variying quality cards.
Classic example:
TBSC 5.1
Playback compares well to new cards (many agree that it is better than the SBLive!) (96KHz)
Recording low for new cards (48KHz)
SBLive!
Decent playback (some say as good as or slightly lower than TBSC)96KHz
Recording was the top in it's time (96KHz)
So if you wanted to play games, many went to the TBSC, but if you wanted to record, many went with SBLive!
This is a brief description (that doesn't even cover the prosumer market). Just get a card that is suited to your needs and couple it with speakers that compliment the cards (good card + bad speakers = bad; bad card + good speakers = bad, bad card + bard speakers = bad, god card + good speakers = good). These parts rely on each other, so get a combo that plays well together.