Late to the party here, but almost certainly 8 ohm. I use a Markbass Mini CMD 121P IV combo with an 8 ohm New York 121 cabinet. Gives a final impedance of 4 ohms to the amp. Of course, we'd need to know the exact combo you're talking about...
All sorted now chaps. Got an 8ohm 2x10 to go with my combo, as recommended by Riccardo at Markbass. Took the lot out last night for a gig, sounded creamy. 😎