Hi @chungjh
I am thinking about moving to a bigger room. The question is Quad 2912 or bigger Sound Lab?
That (obviously) begs the question: how big a room?
Since you asked for an opinion, mine is to go with the next model up (745) in the SL lineup. It will definitely fill the room up and if you listen to orchestral music, it will definitely offer a more plausible simulation of a full orchestra.
I like what I've heard of the Quad, but IMO it's no match...