In my experience when I tried to take my E8600 past 4.5 the temps went way up as soon as I got past about 1.31 vcore and I was never able to get stability. OTOH, at 4.5ghz my system is stable at 1.27v and idle temps of ~0c and 30c load.
The tec seems to cool fantastically until I reach its limit and then everything goes to hell. I think the problem is tec limitation, not cooling.