Pros: I've been searching for a completely silent power supply forever. I didn't test every single one out there but from what I've tried, my results are below. Do'nt expect anything scientific or too detailed though haha After trying out a few power supplies courtesy of Newegg, here are my basic observations regarding their acoustics: 1. Seasonic G-550W Gold. Fan is always on. There is a noticeable clicking noise from what I believe to be the fan. You won't notice it, but from 1-2 feet away it's there. 2. Seasonic 660XP2 Platinum. a hybrid model where it turns the fan on after a certain amount of load (40%?). At idle with the fan off, there's a buzzing sound from the unit. No comments on the fan since I never went above 20% load. 3. Rosewill Capstone 450W Gold. THis is a Super Flower unit which I was hoping would be quiet. The fan is always on. Unfortunately the fan itself is noticeable, more so than the G-550. 4. Corsair HX650. Another hybrid fan made from Seasonic. Just like the 660XP2, there's a buzz from the unit when idle. 5. Corsair RM650. This was the last power supply I tested and if it wasn't "Ultra-Quiet" I was just going to return everything and keep the Seasonic G-550. Wasn't too optimistic opening the box but I'm glad I did! THis one is also a hybrid fan and there is absolutely no noise, no buzzing, no whining at all when on idle/low load . Had to make sure it was working by plugging it into my Belkin Watt meter. I haven't tested the fan yet and probably won't just because I don't think I can hit 40% load to start the fan up.

Cons: None

Pros: Nice black speckled coating. Although may scratch your case.

Cons: The fan is not completely silent. It's too loud if you're looking for a completely silent power supply. I was under the impression this one would be silent since Super Flower (who makes this PSU) has high praise. I ended up getting the Corsair RM650 (although it's $30-40 more) and at idle/low load it's completely silent.

Pros: Warranty, presentation.

Cons: I was hoping this would be a silent power supply when the fan was off but there was a light buzzing noise. Very disappointed. I also tried the Corsair HX650 which is made by Seasonic as well and that one also buzzed. Now i'm looking for a completely silent power supply, and these two hybrid units don't fit that description. I eventually chose the Corsair RM650 which is cheaper, but only Gold and not Platinum certified, and this one is completely silent. There's absolutely no buzzing or noises of any kind when my ear is next to it.