Tripp Lite makes a series of voltage regulator, noise filter, and surge protector. $115-300 on the big A. They're especially designed for computer rigs.
Least expensive plug-in power conditioner that works
I am currently using a Shunyata Venom defender on my main system with good results. I’d like to put a similar device on the power to my Internet modem that’s in a separate room. I notice that there a lot more choices in this product category now. Does anyone have any recommendations that are cost effective and make a difference in performance?