I am looking into buying the Sub to add to my existing x2 play 1 and the Beam which I already enjoy very much. I understand the sub really improves the sound experience for music and movies. My question is should I buy the Gen 3 or go for the older model which now is 145 dollars cheaper? and how do I tell if it is Gen 1 or 2? I cannot tell from extensive google search a Gen 1 from 2?