From the fabulous (and GIANT!) Dan's Data Cooler Comparison:
and specifically from here:
it says that the SK7 does "very, very well with a medium powered fan" (80mm YS Tech) and the same with the TDM fan. It might even stand up to overclocking with a very quiet, low voltage fan -- but it still needs a fan!
So, how about a duct to a 7 volted 80mm or 92mm, or maybe a 5 volted 120mm? With a tight inlet (over the conveniently rectangular SK7), you might just get plenty of air flow with a quiet fan...but passive? I'd be very surprised, though it depends on your use patterns? Or maybe a bit of undervolting on the CPU? I bet this is quite possible to do as far as those "tame" clock speeds -- Intel's latest is more than twice
as fast that clockspeed!