I decided to try running this on full 12V to gain some insight into its full noise level at first. But it was so nicely silent even at full rpm that I saw no reason to slow it down. I had the stock Antec also at full speed. My case isn't really any gamer's case, so I thought it's better to be safe than sorry. Despite being far more silent, I think this Noctua still moves no less air - if not more.

The model is NF-S12B FLX if you are interested.

Although I didn't intend to start a computer part discussion in this thread... It just made me glad that my noisy computer got considerably more silent.