It funny, every time you mention or suggested Delta fan, and everyone hate it, saying it is to loud bla bla. Personally, I love Delta fan pwm. I use 10 of them total for my custom water cooling and love it. Now, I know what you all thinking, You must be deaf. The answer is of course I am not deaf. All the rpm is controlled via pwm and bios.
When I was running a air cooled Noctua NH-D14 my PC is boring. I can't hear a damn thing. Replaced the fan with Delta fan, and I love it. When I was rendering video, I hear the PC noise and i know it is still rendering. When I don't hear nothing, I know my project is done. Now , I understand, every body is different. Just like car. I love my corvette rumble with aftermarket exhaust. Other like it stock and quiet.