If it's sounding like a threshing machine ....... it might be as simple as taking it in for a good servicing with your dealer!
While I have not used a 1600, my understanding is that it is a true work horse and wonderful for FMQing. It just does the basic forward/backward stitches and not fancy work. Not sure how large the throat is??
I loved my Janome 6600 ..... and it is what got me hooked on FMQing. However, I found it limiting, as I was moving on to bigger pieces and did not enjoy the challenge of stuffing it thru the throat.
So no matter what make/model you consider, if FMQing is in your future seriously consider the throat size as a big part of your decision.