I don't know much about this. Say, for example, you're using a head that runs 350 watts @ 8 ohms with a 250-300 watt 8 ohm cab. Will this be bad for the cab (might blow the speaker at high volumes)? Or for another example - a head that runs 750watts @ 4 ohms w/ a cab that is 700 watts? Last summer I blew the speaker in my Bergintino AE112 (300 watts, 8 ohms) w/ an Aguilar AG500 (250 watts @ 8 ohms) so I've been more curious about proper head->cab parings lately.