ASUS SupremeFX X-Fi (just one case, where they use the AD1200 chip if I am not mistaken) doesn't feature an audio processor. AD1200 is just a CODEC. All processing is done by the CPU. Other manufacturers like MSI for example have a similar product that uses Realtek 888D chips.
Hell, I even have on my Dell laptop a Sigmatel STAC HD codec, that is branded as Creative Advanced MB when you pay 20$ extra for Creative software.
Codecs like these can be found on any Creative sound cards.
This products are exceptions and at their core have nothing to do with Creative, they just come with Creative software that uses Open AL. All processing is software based. Asus/MSI have chosen to market them as Creative products because they look as a much more quality products then they really are and add value in the eyes of uninformed customers.
In this cases, you pay for Creative's software which comes bundled with the product.
Here is a link to a PDF that expains it better then I can. You can buy this directly from Creative and you can use it on any form of integrated sound cards (that feature HD CODECS) for like 20$.