surface is everything!
if you want to get closer to ambient, you need a way bigger heatsink
no fan in the world can blow away more as what the HS is able to "transport" away from the IHS and dissipate into the air ... C/W you know. Even freezing cold air would not bring you closer to ambient when the max dissipation capacity is reached.
This is where watercooling beats traditional "air", because a radiator is basically a heatsink with a LOT more surface area.
Depends on the water cooler radiator and the air cooler being referenced. Not all water cooler radiators have more surface area than all air coolers. It still depends on the individual units being compared. Many of the high end air coolers have a lot of fins packed closely together. What you say would certainly be true of most custom water loops but not true of a lot of AIO units.
This of course does not mean that bolting 5 MO-RA rads in series is gonna bring you any closer to ambient if you are pumping +3v into the CPU. Even while 5 MO-RA's could probably dissipate a few KiloWatts
Because the problem moves away from the heatsink/radiator/surface area, the problem moves to the heatsink/waterblock base & the IHS. A square inch copper wb/hs base just does not have the capacity/surface to move that much heat away fast enough from the even smaller chip.
This is where the rubber hits the road, isn't it! The CPU companies need to go back and start making larger cores again for the sake of us overclockers. Down with this smaller fab process stuff!
Now, IF you could only lay your hands on some UnObtainium to make a HS/WB base, but Conumdrum and me have split the worlds stash between us
What is an option thou when using a few MO-Ra's in series, is to stuff a TEC-stack between WB base and IHS
TEC-stack? What's this? "Thermal Electric something"? Phase change?
it takes most people waaaaay longer to get there 
