You obviously aren't an audiophile if you don't understand how this works. Go troll another section.
HDMI carries digital signals which have to be converted into analog at some point and then amplified. Somewhere between your HDMI cable and your speakers there is a DAC and an amplifier.
Soundcards/on-board chips have the primary purpose of converting digital signals to analog signals. On-board sound stages have to worry about space taken up on the motherboard as well as EMI from other conductors on the board. These components tend to be low cost as most motherboard manufacturers (especially ASUS) will expect their consumers to buy dedicated sound cards if the sound quality isn't 'good enough.'
As DACs and amplifier components continue to drop in price it isn't a surprise that on-board sound is getting better. In this case it seems Creative is just rebranding their current offerings.