I have a Quad-SLI setup with a Creative X-Fi. With Quad SLI enabled all I get is snapping and popping, disable quad and it works. I had it in there before but then I had to reformat and it started this. I've tried every driver revision for the graphics and sound card including beta's and i've tried changing the PCI latency. I've also tried it in another PC and it works just fine.

Any thoughts? If anyone knows of a better card too that performs better than the X-Fi, let me know.

9800GX2's - Intel Core 2 Extreme QX9650 - 4GB DDR3 Corsair XMS2

I can't help with your fist question, but I have heard if it happening.
If you want something other than an X-Fi, take a look at the Asus Xonar DX, or if you want a higher end one the D2 or D2X would work.

I've had weird Vista issues with my X-Fi too. For some reason, it works fine, no sound popping or crackling, when using Aero Glass theme, but when I switch to Vista Basic, hello sound popping and crackling. Why the Windows theme would affect the sound card makes no sense at all to me, but it does. Last Creative card I'll ever own.

Yeah creative has small bugs like this that is just pathetic. Their latest patch, there was a bug with a feature, so they just removed that feature instead of fixing it... *sigh

I'm going to try the Xonar I guess.

See if you can get your hands on a beta driver from the 177.xx series. I found that the 175.xx series was utter garbage, and all of my problems went away once I installed the beta that was leaked onto Guru3D's forums. It's odd how my video card drivers can affect my system in such weird ways...

I tried those as well. I'm currently using them right now. I tried every driver version. That's how desperate I am xD

Seems like I remember reading that it was something to do with having cards in SLI that for whatever reason caused issues with Creative cards, but I don't know for sure.