NHT Sub Two Owners

At their closeout prices these subs seem like a steal for music. However, I haven't been able to actually hear them, so I'd like help from owners. 1) Do the units have any hum/hiss when the amp is active and no music is playing? If so, about how loud? 2)How difficult have you found to place themin your room for good response and speed? If you can compare to Paradigm Servo-15, REL Strata or Vandersteens it would be most helpful.