it'll work but you'll not have the best quality, it'll lack bass and can't be at high volume as the onboard sound isn't powerfull enough to deliver high input and that's causing distorsion, i use the Siberia and the G45 version (so i think it's surely the same onboard audio) but i can definately say that i won't use that with a onboard solution...
You can buy a cheap Xonar DG for 24$ on NCIX and that'll work flawlessly as i was running an old X-FI Xtreme Audio with about the same specs (but no more PCI slots on the G45, only PCI-e so i changed) and the sound quality, volume and bass was really good with a cheap card comparing that to onboard, Onboard is real crap, i will never use onboard again as any sound card is better even cheap...