No idea about mains suppressors/conditioners. My amps have always just run on what comes out of the socket.
As for kettle leads, try to go for the standard connectors - without the gap between live and neutral, as they are the proper plug for the job plus kettle leads tend to be quite short. As for the fuse, the small glass one in the back of your amp will be lower rated than anything you stick in the plug. I just use a 13A one in there. Your amp fuse is the one doing the protection