My Zu Omen Defs are already 8 ohms, however, I've read that people with Zu Souls use the resistor with great results. My Omen Defs are rated at 101 db efficiency. The review measurements generally palce it around 96-97 db, which is still really sensitive. I'm hooking up the amp later today. I just with there were a better way to turn the thing on and off. In the past, I've tried those "master" power strips, but find that they add noise. I currently run all my components to a Torus power conditioner/protector.