It does make it quiet but instead of going with water cooling S5 go with Avalon 4.1's.  If you need quiet they will do it with no modifications.  

Watercooling sounds great but I can say it truly is a pain to mess with compared to normal fan's.  Listen to videos of 4.1's they are about the most quiet stock miners with just underclocking. At least that I have used (I'm talking full miners like Dragon 1T or newer, not including stick miners).