btw eventhough u have balanced cables now, did u check out if your gear is balanced? speakers and soundcard that is.

BTW heres a stupid advice: u can put a capacitor direcly into your inlet.... high frequency noise from the power source (your homepower-net or what to call it, im terrible in english) will travel through the capacitor from + to - as it is basically a high-pass-filter with less resistance in the high frequencies than your gear. then the noise will magically disappear before entering your gear. electricity goes the easiest way and the noise will therefore go through the capacitor. u have to calculate the size of the capacitor yourself, ur supposed to be filtering everything above 50Hz but since the noise is high u can probably use a 1000Hz highpassfilter. u can also make a second degree filter using a inductor/coil in serial-connection with your gear too. This is illegal as far as i know btw but i did it once and it worked.