Looking for a bit of advice here

I’m using a high spec PC for my mixes - 3.2Ghz Dual core - 1 gb ram
but am getting glitching on the audio when doing intensive tracks. I’m guessing this is down to the onboard sound card, so am considering going to an external usb, or firewire type.

The unit I have in mind is an Emu-0404
Can anyone recommend this, or have any other suggestions?