However, this can give a rough ballpark figure on the cooling efficiency of the heatsink with the stock fans (at certain airlow).
Yes, at certain airflow: at a different airflow (the one which matters for SPCR readers, for example) it can be different, so that prediction (the rough ballpark figure) cannot be used, or even better, that's what I meant.
Further, if one keeps the same airflow (m3/min, CFM) and just finds better / quieter fans, then it is probably possible to tweak the sonics (esp. the frequency spectrum) one way or the other, without affecting the cooling significantly.
Quieter fans have a different airflow (likely inferior), so that prediction about cooling prowess doesn't necessarily apply: with a better sounding one (bearing noise and the likes), YMMV.
Of course, I'll still try and compare them against the best of Prolimatech, Scythe and Noctua coolers.
The proof of the pudding is in the eating.
I was also considering trying the NoFan series (but with a very low spinning, large fan attached to the top of it), but it seems that NoFan CR-series has no LGA2011 mountings.
AFAIK the NoFan is not suited to cool any LGA 2011 CPU, so I guess that's why they don't supply such mountings.
You might give a look to Zalman FX-coolers also (I dunno whether they provide 2011 compatibility).