Hey Guys...I've been reading this forum for several months now since having my insert installed (Hampton HI300). I know that I have a non-cat insert and was advised that they are much more simple to learn/operate than a cat insert (i.e. HI400 or Grand Voyaguer, etc.) But what exactly is the difference between how a cat & non cat insert/stove works? What are the advantages/dis-advantages to cat & non-cat?