Simple fact is, Noctua's are great fans and are not overrated.
I'm using Chromax A-14's for myself, but I considered both the Be Quiet's & noiseblockers to replace my cases stock phantek's. Unfortunately, first I tried to cheap out and try my luck on some Arctic Bionix F140's first. They simply vibrated so much within my case, I couldn't stand to use them. So, eventually I ended up with Noctua's because they have a much lower dba rating at max specified RPM than either the Be Quiet & Noiseblocker.
From personal experience, the only noise I hear up to 1,100 rpm is air and I rarely have the need to run them over that speed.