I own AKG K271 & Sony MDR-7506 (along with KRK VXT6) for music production, all connected to Mackie Big Knob. I plan to purchase DT880 600 ohms as a step-up. A couple of questions:   1. Big Knob's headphone out impedance is 150. Can this adequately drive 600 ohms cans? (How should I calculate...