It's almost ironic that coolers like [the Thermalright Silver Arrow] are becoming available just as processors transition to designs that may ultimately render them unnecessary; even overclocked to 5GHz, an Intel Sandy Bridge 2600K doesn't need anywhere near this level of cooling.
I have an H100 on a corsair obsidian 800D case. I must warn you that it is VERY loud because you hang it on the top of the case (and therefore you can hear the fans much more). On the "low" setting,however, it is very silent.
Personally I OC'ed my i7 930 (2.8ghz stock) to 4Ghz with 1.375v and the stress test temps to max 83degrees in a 20-24degrees room, so yeah it has alooot of cooling power. Also I bought an aftermarket thermal paste (IC diamond) to improve the contact, but i'm not sure if there was any improvement cause I installed it right from the first time.
Never had an H80 but i guess it can also do the job, maybe not at 5Ghz though.