Noctua's out, I'm not paying the tax. They're something like €28+ a pop over here. Compare it to Phanteks - €14.
You did mention "wide RPM range" so if you can find an A14 iPPC-2000 for about 25EUR then IMO that's a pretty good buy. Moves more air than the A14, is black (except for the vibration pads), and is a physically stronger and tougher fan than the A14, and has a wider RPM range that you can tweak to your liking depending on what sort of airflow/noise you want. Where I am right now the regular A14 is $33, the Chromax is $33, and the iPPC is $37 which makes the iPPC a no-brainer since I've seen it as expensive as $55 at times. Chromax is literally just a repainted A14, value is kind of questionable if they're not the exact same price.
But if it's just one rear exhaust fan, you could make do with just about anything. I heard that Phanteks is indeed the underdog in fans so it's hard to beat. You could also look for the Silent Wings 3 140mm; the performance as with most Be Quiet fans is underwhelming (super quiet, but not great), but their anti-vibration mounts are quite good, and I prefer the BQ clip-onto-the-fan mounts to both the Noctua SAV2 and AV2 pull-through rubber sticks.
