I sometimes use my iMac display routed from the Mac to the HDTV via DisplayPort-to-HDMI.
When I tried my own AF Filter Box and plugged my computer in it (but not the TV, hadn't though of that at all), the image became clearer (the fonts were more legible). This was unexpected but fun to observe.
Ideally, I should re-do all my power cords for the video side of my equipment too.
I couldn't give you a definitive answer. I would suggest you replace the power receptacle that everything is plugged into as a first step to see if it helps. I think Mapleshade, MIT and Furman have some nice ones for less than $150. Make sure you get a 30 day audition period.