The question isn't whether the Noctua is a good heatsink, it is, but the problems that pushed me to select a h100 are still valid. The first reason is mass attached to motherboard.
Easy solution for this if you're building your own case: bolt the cooler to the mobo tray. All you'll need is long screws, spacers, and four more holes in your tray. There are variations on that theme that can be universal solutions, as well.
But I find it curious that you're worrying about mounting a giant, aftermarket heatsink to your mobo while blithely strapping another one to your video card.
The other issue is the direction of airflow, a c14 would pretty much require a side intake to perform anywhere near as well as it tested.
I agree with that, but I've ready way too many scathing comments about those watercooling-in-a-can coolers (several specifically about the H100) to every try one. The best option, IMO, is to just widen the case enough to fit a 120mm tower heatsink. I know you want to keep the case small, but an inch or two in width seems like a small price to pay for the convenience, performance, and reliability
But if that won't work, why don't you skip the halfway measures and go straight to a full-fledged watercooling rig? I don't think it's that much more expensive, and If you use a universal GPU waterblock, you could save yourself a broken PCIE slot along with a broken mobo. When I looked into switching to water myself, I priced out a rig that could handle CPU+1xGPU for ~$200. It would be a lot less if you milled your own waterblocks, and that should be a breeze for a guy with access to a CNC laser cutter.
P.S. -- Woohoo! I'm no longer a lurker. Took me long enough.