That will be a problem actually. Most PWM implementations suffer from noise at some voltage ranges. The ML series seem affected so far.
Personally, I would visit the Enermax site, check what's available and see if a local dealer that accepts rmas has any of the ones I want available.
Quality control is very important with mag-lev fans and nowadays manufacturing quality is inconsistent, meaning that you might get a dud or two.
The good news are that if the fan doesn't have issues after some months, it won't die for at least a decade or so.