I'm also looking at slowing down the Bitfenix case fan i bought for my new rig. There is a dial on the case itself, but i think the fan is still running louder/faster than it needs to. Mind you, i'm using the top fan port so it's also possible the noise is just more audible as in the past i've used front and back fan ports.
I'm going to play around with the location and in doing so, close off the top fan port with (non glued) acoustic material as well.
Other than that, i have a fairly silent system.
Here's the specs (purchased pre-Christmas during early sales):
Intel Core i5 4670K Unlocked Haswell Quad Core 3.4GHZ Processor LGA1150 6MB Cache Retail
ASUS Z87-PRO ATX LGA1150 Z87 DDR3 3PCI-E16 4PCI-E1 CrossFireX/SLI SATA3 USB3.0 DVI HDMI
Corsair Cooling Hydro Series H80I CPU Cooler System LGA1150 1155 1156 1366 2011 AM2 AM3 FM1 FM2
Patriot Viper 3 16GB 2X8GB PC3-12800 DDR3-1600 9-9-9-24 1.5V Dual Channel Memory Kit - Black Mamba
Western Digital Caviar Black 1TB SATA3 6GB/S 7200RPM 64MB Cache 3.5IN Dual Proc Hard Drive OEM (storage drive)
Samsung SSD 840 Pro - 128GB (my system drive)
MSI GeForce GTX 760 Hawk Twin Frozr IV 1111/1176MHZ 2GB 6GHZ GDDR5 DP HDMI 2DVI PCI-E 3.0
LG GH24NSB0 DVD-RW 24X SATA Black OEM
Corsair Graphite Series 600T Special Edition White Mid-Tower Case ATX 4X5.25 6X3.5INT USB 1394
Seasonic X Series 750W KM2 ATX 12V 24PIN 80PLUS Gold Fully Modular DC-DC Power Supply w/ Hybrid Fan
