Probably one of those things that because the only place to get SoundMax/ADI drivers is from the motherboard manufacturers, as ADI doesn't release drivers for general sue. That and it is up to each manufacturer to release any updated driver they get from ADI. Then there is the problem of which of their motherboards they post the update to.
Asus is famous for this sort of thing (there are a few threads here about this sort of thing with different motherboards that come with the SupremeFX sound), and not just for audio drivers. They have a very bad habit of only posting the updated driver(s) to currently available motherboards, and even then not always.
Probably about the easiest way (not really) is to check what is available for your specific motherboard, then to look for newer boards that use the same audio chipset and see if any of them have received an update.
The big difference between Realtek/Creative and ADI, is that the others have a semi-unified driver that they put out, just depends on which card/chipset you have as to which to use. Even C-Media puts out a unified driver for most of their current lineup of audio chips, the only difference with their reference driver over what is available from the card/motherboard manufacturer is it is missing the manufacturer's specific software/control panel.
