Well these are all good coolers in their class. All are bolt down, and only the Thor Hammer is HDT.
Though I would place them is performance (ascending):
CM V8 : Thors Hammer : Scythe Mugen
Again this is based on my reading about these. For sure CM V8 is the lowest cause its fan does not do the job, though the architecture, 4 layered towers is the best. Scythe Mugen has the best heat pipe system, where as Thor is HDT.
My choice is with the Noctua NH-D14, whose link I put on the first page of this thread. It is expensive, a bit shy of 5K. (Expect a review soon..hint hint).