After digging around a bit on other forums where the GA-Z77X-UP5 TH motherboard is pretty popular, I have found a few people who used the Noctua behemoth with no issue... aside from having to use low profile / no heat sink memory, of course.
I too was looking to use the NH-D14 for my build, and--as long as the case is roomy enough--it looks like we're good to go.
EDIT: My bad... misread the title as *D*14, not C14. I'd assume that the C14 will fit just about anywhere the D14 will; the physical dimensions are similar according to NewEgg details pages.
If you try it, be sure to come back and let us know how it worked out! Let the rest of the internet benefit from your experience.
Well, I'll search around for the right cooler this time... maybe find someone else who's used it. Looking through the Hackintosh communities mostly, as they seem to fancy the UP5 TH for stability/compatibility... in case you're interested in digging around for info yourself. =)
Haha, yeah, I'd suggest you don't. Sure you could do it fairly easily, but there goes your lifetime warranty...
Unless you've already got the RAM, low profile is a better choice anyway; most people (and tests, from what I understand) agree that the heat sinks are unnecessary for stable temps (unless you're going for insane memory overclocks), they are more forgiving of hugenormous CPU coolers, and (in my opinion) look sleeker than memory with fins sticking out like saw blade teeth.
Sorry I don't have a more concrete answer for you, but I *think* you will be just fine -- with the Asus or the Gigabyte mobo. I've found people using the NH-C14 cooler on the "older" Gigabyte UD5H (which also has fair-sized heat sinks on around the CPU) and they seem to do fine. Not certain about the orientation you asked about, but you're not likely to find that out online.
If you want to be sure, you could always just get two of those slim case fans for each side of the cooler. Or, if your case allows the height, just put the fan on the "top" of the cooler only. A higher CFM fan could still do a great job while being fairly quiet, if you find the Noctua fans inadequate (or ugly). =P