The further away the ANALOG part of a sound "solution" sits from the motherboard, the better it's likely to sound.
Most SoundStorm implementations use a Realtek ALC650, which has VERY crappy analog quality. On the other hand, the Asus A7N266-C, which had Sigmatel codecs sitting on an ACR riser card, sounded beautiful.
The cMedia gear is okay when it comes to analog audio quality - but Sound Blaster Live! and Audigy series of cards support acceleration of 3D audio rendering, which increases your frame rates while gaming (the CPU is free to do game-related tasks rather than figuring out how the half-dozen bullets whizzing past your head should sound like on your two speakers).