A small update on my delidding adventure:
It turns out that my Hyper 212 Evo had a small indent in the base (my fault I'm afraid!), so I finally got around to buying a new cooler and decided on a push-pull Arctic Freezer i33 Plus, which is only about €3 more. I had my eyes on a Scythie Mugen 4 PCGH (push-pull w/800 RPM fans) for a good while, but figured that the i33 Plus would be just as good and a little cheaper.
Since I had to unmount the motherboard to switch the back plate mounting bracket anyway, I figured that I'd pop the lid on the CPU again (it was secured with two small drops of superglue) and see how things looked. I cleaned off the CPU package, die and the heatspreader and checked that the CPU looked fine (it did).
Then I reapplied the Coollaboratory Liquid Metal Ultra on the CPU die and put a couple of drops of superglue at opposite corners on the CPU package and put the heatspreader back on, tightened the CPU mounting clamp and mounted the i33 Plus with four thin stripes of MX-4 (one stripe for the length of each heatpipe in contact with the heatspreader) per the excellent instructions provided by Arctic.
Cost: €42.50 including VAT. The results? Excellent as far as I'm concerned. And the fans turn off when the PWM signal is at <40% duty cycle, making the cooler completely silent at idle and low loads.
Intel BurnTest results:
Stock @ 3.9GHz: 53°
C (fans not full speed)
OC 4.5GHz@1.3v: 73°
C (a drop of 7°
C compared to the Hyper 212 Evo)
In other words, I'd gladly recommend the Arctic Freezer i33 Plus to a friend.
I *may* be able to drop the voltage *slightly* from the current 1.3v, but the CPU seems to be more stable at lower voltage during stress testing than when doing normal tasks (which seems somewhat counterintuitive).