I wouldn't get a Nvidia motherboard. They usually 'crackle, snackle, pop' on them and when you call Nvidia, they will say it's the sound cards fault. Then when you call Creative, they will blame Nvidia. Personally, I would go with a Intel motherboard and get no problems. I have a X-Fi Sound Blaster XtremeGamer with my Gigabyte P35 DS3L. It works perfectly.
I have a X-Fi Fatal1ty FPS on a Rampage Formula and it works perfectly. I did have the same card with my P5N32-E SLI and it was the only thing that didn't cause me problems with that board.
Just an afterthought... You would be better off replacing that 8800GTS 512 with a 48xx or 9800GTX+. More performance for the same price or lower...
Ok, I'll stay away from nVidia chipsets (and focus on Intel P35/X38/X48).
And I'll check the 9800GTX prices.
If you decide to get an Intel based Mb you should really check out the 4850 or 4870 so you can CrossFire if you need more power in the future. The 4850 is more powerful in many games than the yet to be released 9800GTX+ and can be had for well under $200.