Any suggestions to quiet my powerhead?

I'm just getting water into my 40 gal. tank and will be putting in the sand and live rock tomorrow. I put the powerhead (Via Aqua 480) in the tank last night to make sure it works. Well, it works, but I"ve got one kind of annoying problem. The thing vibrates when it is suction cupped on to any side of the tank or even gets close to the sides of the tank. If I suspend it by the power cord in the center of the tank or hold it by hand it's quiet as can be. Does anybody know if this will change once I get the tank full of water (currently 15 gallons in) and/or add the sand or rock?

Can't really hear it with other stuff going on in the room, but at night or other quiet situations it is very evident and kind of annoying.

I think I know what you're talking about. Right now I'm just sticking the pump right on the side of the tank with the suction cups that were attached to the bottom. There are no mounting accy's on the pump right now.

I really wouldn't mind the problem so much except for the fact that the tank is in my bedroom so sleeping with that friggin' noise is going to drive me up the wall...hehe. Unless I can get used to it quick. There's got to be something I can do though. My friend has a SW tank and he's got his ViaAqua stuck to the side of his tank and it makes no noise. Maybe it's because he's got a glass tank and not an acrylic one like mine?

All's well now. I think once I got the sand, rock and the rest of the sand in it did the trick. Can't really even hear it now at all. I think everything else in the tank helped to dampen the sound.