^ +1 on Scythe Mugen 2 Rev.B (it's being discontinued).
Being replaced by the Mugen 3 which I heard performs almost the same or a little better (but not by much). It looks a little smaller than the Mugen 2 (as well as lighter) based on the specs given (at Scythe-USA) and the review I found at:
Mugen 2 specs (Heatsink/no fan): 130 x 100 x 158 mm - 870g
Mugen 3 specs (Overall - Heatsink with Fan) 130 x 108 x 158 mm - 826g
According to the specs of you case, you should be able to fit it if you have no fan
CPU Cooler Clearance:
143.5mm (with fan)
168.5mm (without fan)
I have the Scythe Mugen 2 Rev.B and got a 4.0GHz OC @ 1.195v running cool in the 30-35'c zone idle. Fan profiles set to silent in BIOS. Fan controls on the case for the 3x AP 180mm fans set to low. Room temp at the time around 26-27'c before sleeping.
My P95 blend for ~7 hours
Showed no errors. I see avg voltage at 1.189v, so I might push voltage down to 1.190v.
Case: Raven 2 Evolution (RV02W-EW)
MoBo: Asus P8P67 Pro
RAM: G.Skill Ripjaws X 8GB (F3-12800CL7D-8GBXH) - manually set to 7-8-7-24-2T @ 1.55v (a little undervolted from 1.6v)
Mind you, for the Asus board, I use the second and fourth slots which is what the manual suggests. This works fine as I think I will have problems fitting RAM in the first slot.