No need to whip them out, just pop the bonnet and look at where the mounts are sitting, if one is above the other, it's the higher of the two which is kapoot!
I'd recommend changing them in pairs, and go for the slightly stiffer G60 versions if you're using coilovers.
As for the humming, sometimes your ears can play tricks, no rabbit's out of hats, but sometimes it sounds like the front, but really it's the rear.