On the 1600 machine, check to see what TYPE of needle you can use. If my memory is correct (and most of the time it isn't) you have to use the DBX needles.
Check into the Janome 6600P. Fantastic machine. I've had mine for about 4 years now and have never had to have it serviced! I use my machine DAILY and it sews like a charm every time no matter what I decide to use for fabric.