My three year old PC built using an Antec Sonata case started developing an annoying whine. I tried ignoring it for quite a while hoping it would just go away. No luck. Eventually traced it to the Antec power supply that came with the case. So after consulting the SilentPCReview website, I bought a Seasonic S12-430 to replace it.
I'm very pleased with the Seasonic power supply. Very quiet and excellent cabling and connections. The only thing that would make it better is if you could unplug unused cables and monitor the PSU fan speed.
After replacing the power supply, I discovered a new problem. The old Antec power supply cleverly controlled the case fan so that it ran quietly unless the system got hot The Seasonic didn't provide this so now I had to run the fan at a constant 12V and it was proving itself a noisy fan.
Back to SilentPCReview with the idea of replacing the fan. After drooling over the pricey Noctua fan that I couldn't justify buying, I bought a few Nexus fans from Novatech at half the price. The Nexus fan proved much, much quieter at 12V and I now have the option to drop the voltage and make it near silent. I can certainly recommend these products.