Finally, I tried install NH-D12L today. It fit 8950. Like other posts, I have to buy M3x20 screws to install the mount. Temperature down 10 degree+ on idle. However, I don't know why it can't detect fan speed even the original fan.   [IMAGE]Noctua NH-D12L  
Checked the discussion here, the height limit is about 145mm for 8950. I want to replace Noctua NH-D12L. It is exactly 145mm. So, is it really fit this case? Thanks!
XPS 8950, CPU cooler height limit