Pretty much any line filter is fine. Just search for a 10A+ AC line filter, most games have one already installed but they can go bad, caps age and there is nothing you can do about that.
As far as hum goes, the AC line filter might help but transformers hum. Its kind of what they do, its possible the glue that holds the plates together is a bit loose and you are hearing the plates vibrate at 60hz. if that really bothers you, buy a new transformer. I would say leave it alone, if it works, don't touch it.
yeah but not just the plates,, the knives and forks rattle too