Pirakaphile
500+ Head-Fier
If you want to get an amazing power conditioner and are willing to do a bit of searching you can find industrial strength Topaz Line 1 or Line 2 Power Conditioners for a steal. These things retail for up to thousands, but can be had used for cheap. There's always a risk they hum a little bit, but when you're getting something for 10% of its price then that's a risk you might want to take, and with headphones you'll be unlikely to hear it anyway. I have two of these protecting the two channels of my stereo setup and I rest well that I can leave it on 24/7 and never worry about anything getting through. .
Here's a number that are on eBay currently. They're used and sometimes a bit beat-up, so they're not audio eye-candy, but they were built for very sensitive industrial or laboratory equipment, so are very well made. YMMV of course, but I love these things.
http://www.ebay.com/itm/Topaz-Line-2-power-conditioner-model-02406-01P3-1kW-used-works-/251656503126?pt=LH_DefaultDomain_0&hash=item3a97e57f56
http://www.ebay.com/itm/Topaz-Power-Conditioner-4-line-output-computer-electronics-protection-/291432902970?pt=LH_DefaultDomain_0&hash=item43dac1313a
http://www.ebay.com/itm/Topaz-Line-2-Power-Conditioner-120VAC-6-8-6-Hz-8-3A-Model-70303-/191433180734?pt=LH_DefaultDomain_0&hash=item2c924e863e
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2055119.m570.l1313.TR0.TRC0.H0.Xtopaz+power+conditioner.TRS0&_nkw=topaz+power+conditioner&_sacat=0
http://www.ebay.com/itm/Topaz-1KVA-120-Volt-10-Amp-Line-2-Power-Conditioner-02406-01P3-/191542260264?pt=LH_DefaultDomain_0&hash=item2c98cef228
http://www.ebay.com/itm/Topaz-line-2-power-conditioner-/281652882186?pt=LH_DefaultDomain_0&hash=item4193d1eb0a
They tried pretty damn hard to make some of the most generic and boring looking pieces of equipment on the market, didn't they? I like the prices, and I'm trying to find specs on their site.