Yes it will sound better.
I've already done that exact comparison on a rig.
The only drawback is if you have Win7 you might not be able to install the full Audigy suite with all the goodies.
Still sounds better then ALC 889 though.
ah the dedicated Audigy 2ZS will be far better than the onboard. I wish i hadn't fried my Platinum 2ZS...loved it every step! But yeh the drivers will be the first hurdle and then the software installation/usage on a win7 OS. Although you COULD try and run the programs via compatibility mode.
Not so fast, the 889 chipset offers about the same signal quality then the Audigy 2ZS...(108dB for both, apparently), so its more signal processing then an actual step up in quality. Audigy has more features built in though.