why cant you get a higher amp 12v p/s to cope with the heat bed instead of changing everything to 24v!!
What noise are you referring to? I've read some posts about steppers making annoying high pitched noise when idle but powered, which these don't make, but they do make 'noise' when they're moving, although I'd say it's nothing annoying and is a 'noise' that I'd consider normal for operating motors. Plus the supply voltage shouldn't make a difference to them, as best I can tell, they seem to actually run off 3.3v or 5v, so a voltage regulator on the controller would be knocking the input voltage down to what they need.