Granted, it's not a life altering experience but it is expensive and I'm on a fixed income so I want to get the best bang for my buck and get it right the first time (keep in mind this is my first build) since it is going to have to last a while. Also keep in mind I only know enough to be dangerous. Different people have different ideas of what silence is. I get annoyed when the little fan in my notebook ramps up every now and then. Even my ceiling fans on low sounds loud. I have replaced the fans on my case with Thermaltake AF0018s. They are reasonably quiet unless I run them full blast (even then, they aren't too bad).
The last two posts have made up my mind, btw. I'll get the i7-3770K for future proofing (such as that is) and because I can turn off the hyperthreading if need be.