I'm using the stock fan it came with. It seems fine to me, even set on "high", it doesn't bother me at all.
As for sound, I'm using the onboard sound. Someone told me it has soundstorm, and it seems to sound just as good as the sound on my nf7-s (soundstorm). And, yes, i believe it supports dd 5.1. The box also has optical in/out on its backside.