I've had a couple of power conditioners and.. without success.. these cheap strips are only to give you a better manual accessibility in your rig, so that everything is lined up in a decent way but it does not solve the hum/undervoltage issue, so, if someone noticed that their sound is tighter with a 20GBP strip, it's all in their heads :) these are more like surge protection units which have a fuse that kicks out once there's too much juice in the socket..
good units with hum filters that have AC voltage stabilizers that really work are really slightly more expensive..
i stopped using these power strips cause it was no good and was really pointless except the fact you can power up your rack units and I bought one thing that looks like a transformer that I have to carry around, but it works very well and i dont care :) ... it was one of the cheapest i could find and it cost 160e :)