Yeah the Audio changes in Windows Vista basically killed all third party hardware acceleration. It is all done in software now. Realtek is all you need from a feature point of view, all the benefits are in the backend (DAC/Amps) and maybe some fancy fake audio. Most people won't care, I would argue that most people likely only use USB headsets anyways (which use the same 10c Realtek chip)Definitely not required as the Realtek audio chips on basically every motherboard is a "DirectX compatible sound card".
I personally don't see the point of a add in card at this point when external AMPs/DACs are exceptionally good, dont take up a slot, are fully isolated and can be moved between machines and even to cell phones if required.