well, the best case fans tend to be noctuas... just because of all the air they move and how they do it silently. just pick the size you want... and the type of power connector you want (4 or 3 pin). I have 3 in my case. thought i'd hate the color, but it turns out the color of those fans are so neutral you don't really notice them. (i have a black case with plenty of mesh and windows, so you can see the fans if you look for them)