The best thing I have found myself on my system is buying a BT Mains Conditioning unit off Ebay, and plugging that into your system. With them you can use any old kettle lead if you want.
It consists of a big mains transformer, (they do various values from 125VA up to 500VA units) and some large mains capacitors and internal overload protection. Cost around £40-£60 when you can find one.
You can buy conditioners brand new off the likes of Russ Andrews, but they cost up to £2800!