[quote name='gilmour' post='260643' date='Aug 12 2008, 10:01 AM']You can do this, but I think I'm right in saying that you'll get uneven power distribution, with more power going to the 4 ohm cab (and thus more volume), but the head should be fine.[/quote]
With a 4ohm and 8ohm cab with the amp putting out 675w, the 4ohm cab will produce approx 450w and the 8ohm cab approx 225w.