If a head unit only states that it has 45 watts of power for 4 channels, is it a waste of money to buy speakers with more than 45 watts of nominal output? Will quality suffer?
Your ears will suffer when you turn up the vol of the hu all the way. I wouldn't consider it a waste of money to invest into some good speakers, if you have decent hu and you might upgrade an amp later you wont regret it. Of course the full potential isn't used till then. Besides 45 W rms is quite normal for car speakers.