Monster makes a filter just for subs that plugs into your wall outlet. I think the model number is SW200. I think this should be the minimum you consider unless you want a power surge or lightning strike to take out your powered subs.
Plugging powered speakers in....??
For those of you that have a powered sub in your tower loudspeakers and need to plug them in..... what would be the best way to go about this? directly into the wall? or use some type of filter/powerstrip?