I have used mugen 2 on x58-ud5, 790xt ud4p, 790gpt ud3h, biostar 790gx a3+, p55 ud4p, p55 gd65 without any problems. You have to install fan after installing fan. On amd mobos you could use the farther ram slots.
I have got noctua d14, it's huge and doesn't perform much better than scythe mugen 2. Just two degrees better on b55. mugen 2 is great VFM.