correct set up

I have a nait 5, cd5 with mordaunt short speakers - and am extremely happy with the sound at the moment.
However i have just moved house and have noticed a very faint hiss from the speakers when no input is playing - this is audible with or without volume turned up. Do you think i have set it up incorrectly or am i just ultra sensitive in my new surroundings?

Also i never turn off my cd or amp - is this a good idea?

thanks
Steve