Well, I have never used hte A7N8XD in an overclocking system, but it seemed pretty stable on my uncle's computer...punkd didn't want to overclock (then again, he just got through a whole new setup because a PSU killed it all..)
There are some voltage limitations on the A7N8XD if I remember right, which you would need to do a volt mod....don't know of where I would find this information since I can't think right now..
I have a NF7-S Rev 2.0 I like it, I wouldn't say its the best board I have, but it is definately a nice board. Soundstorm is actually quite nice, the quality is nice, might be able to be better, but I don't know becuase I have a setup that isn't the "best", z640's. Nice but, certainly not the best.
The NF7-S has a max VDD of 1.7 (there might be a volt mod for it two, hell if I know), which I find sort of disheartening, but hey, like I said there is probably a volt mod for it somewhere around here...
I have never heard sound through an Audigy 2, so I can't really compare it to SoundStorm, but SoundStorm is nice like I said above.
Good luck in the decisions, and have fun w/the new parts
Fold and Frag on
Brian