What's the difference between these two. I'm looking at two power amps that are from the same company, have the exact same specs except the earlier model is ULTRA and the newer one is ULTRA2 and weighs 4lbs more (116lbs). I can't find anything that will tell me what had to be different in order for it to be certiffied as ULTRA2. And of course the most important question is: Will I hear a difference?