The fan polarity being reverse is because silverstone decided to install the fan backwards. Your guess would be as good as mine as to why, I suppose it's to show the label of the fan from the outside of the unit. The placement and way it's wired does draw cool air in. Perfect orientation in my SFF SGPC K39. Draws air in from the bottom of the pc and exhausts it out the top without needing additional case fans, which would. . . add noise.
I tried to remove excess noise by mounting the psu with rubber washers. It reduces it nominally, 1-2db. If i can find something suitable I want to place a thin rubber sheet under where it mounts in my case. Still i measured 51.7db at 18 inches from my case.
The other benefits, 80+gold and total wattage, of the PSU outweighed the noise level for me. Many factors can reduce how loud a computer is and how tolerable that noise is. If you are concerned about the noise level first measure how loud your air conditioning unit is and gauge from that SPL.