I think it states in the manual that you can use a 4 ohm cab - from memory it says use an 8 ohm to 16 ohm but then states you can use a 4 ohm in a separate sentence.
Found it! Yes, at first I was a little confused about the structuring of those paragraphs, but...
4 Ohm is possible. You need to be aware, that in that case the power is limited to 600 Watt. Theoretically the power amp could deliver even more at 4 Ohm. So as soon as you reach that 600 Watt ceiling you hear short sound breaks. Nothing will get damaged. Normally, you stay way below that power limit.
I think I get it. So in the same way that when the amp is run at 16 ohm the wattage is halved, when it is run at 4 ohm the wattage is doubled? However the poweramp can't handle putting out that much power, so it automatically cuts when 600w output is reached? Then the answer is yes, no problem running into 4 ohm without destroying things, just get familiar with how much you can crank it with the combo.
Thanks for the help peeps!!