I got 3 dimmers from HD in the $10-15 range. (Really all they had in a 3way dimmer.)

Two of them have been installed and they, not the lights, produce a slight hum as the lights are dimmed. The dimmer the more hum. If there was background noise in the room, tv or radio you would probably never notice it. Normal?

Also while turning one off, since i dont have cover plates on yet, I could feel heat from the housing. They are not dimmed while I'm working in the room. Are they supposed to get warm, noticably warm?