Not very important I imagine. It's hard to find gear today that is noisy when fed quality electricity. Most current noise issues revolve around dirty electrical feed issues. Different manufacturers may have different signal to noise numbers, but I doubt you would be able to tell which number belonged to which component by listening.
Outside street noises are at much higher levels than noises within audio gear, even in the countryside.
Outside street noises are at much higher levels than noises within audio gear, even in the countryside.