Getting an amplifier with variable speed fans should be sufficient. If the fans are working hard enough to be at full tilt, that generally means you are pushing enough SPL that the noise of a fan shouldn't be noticeable.
My Crown iTech HDs are nearly silent at idle. When pushed the fans kick it up a notch, but still not bad.
My QSC QLD amps, however, have much noisier fans that are ALWAYS on, even when the amp is off! Not a huge fan of the design.