You could stick with the Silent Wings 3: you probably won't notice much of a difference in temperatures, but it is a lot louder than (for example) the equivalent Silent Wings 4 or the Pro running on medium. And even when you stick the Pro on high it comes in just a fraction higher -- I'm talking 0.1 degrees or should I say 0.1 decibels quieter -- than the Silent Wings 3, but performs better, so I think you've got something for everyone here.
Tech For Techs has published a Youtube review of the Silent Wings 4 140mm PWM and Silent Wings Pro 4 140mm. The reviewer is quite happy with the noise/performance-ratio of these new fans and highlights the flexibility that the speed switch on the Pro gives you. The fans have earned the Highly Recommended award.