My speakers are rated for 8 ohms nominal impedance, but have a low impedance of about 3.9 ohms. My old receiver wasn't rated to be 4 ohm stable and my new one is. I know there are other factors (i.e. also jumped from 90 watts to 135 watts per channel), but there is no comparison in sound. I don't know if 4 ohm speakers have as much variance as many 8 ohm speakers do.
If you find an 8 ohm speaker that you like I don't think I've ever heard anyone claim to like the sound of all 4 ohm spekaer more than all 8ohm speakers, but the 4 ohm speakers can be more difficult to find quality amplification for.
If you find an 8 ohm speaker that you like I don't think I've ever heard anyone claim to like the sound of all 4 ohm spekaer more than all 8ohm speakers, but the 4 ohm speakers can be more difficult to find quality amplification for.