There are a few different products out there - power bar (outlet multiplier), surge protector, Line conditioner, UPS (Uninterrupted Power Supply).
I recently bought a Monster Mk3500 or whatever it's called. It is a pwr conditioner, which filters out noise and regulates voltage. Monster is generally overpriced but they were closing these out so it was a better price than others. Here's what I noticed: My TV's menu screen did not jitter after installation. My subwoofer did not hum.
So yes, they can help. At a minimum, I would get a surge protector designed for home theater*. If you notice any hum, or other audio/video noise, get a line conditioner.
*I have read that surge protectors made for computers can limit current to your amp and reduce system performance.
2001 Jet Black ///M3 6MT rolling on 19" BBS CH's | PSS-9 suspension | UUC Swaybars | K&N CAI | Cold Weather Pkg | Pwr Seats | HK Audio | Homelink | DIY rear parcel shelf rattle bolt fix
RIP: 2004 G35 coupe 6MT | Diamond Graphite | OEM Brembo's | Z-tube, K&N, Plenum Spacer, Stillen Sway Bars