Your Belkin gold surge supressor already has some degree of RFI/EMI filtration built in even if it doesn't specifically tout it. I would first check out what Paul Scarpelli suggested which is to see if the problem goes away if you plug your stuff into a different circuit. If you have to, just temporarily run an extension cord to do this. Also, I'd check to make sure your outlets are properly connected. Home Depot and other places sell a little device that's around $5 and tells you if there's a ground problem, if neutral and hot are reversed, etc. The problem you have might be air born and if that's the case then no power conditioner is going to save you. So, before you go out looking for expensive band aids, you need to examine the basics first.
"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House