I, personally, would not get an NX100. That controller is 4 generations old. I would get a YRC1000 or a DX200 worst case. With the NX you are going to run into the same problem in 5 years or so. The NX came out in 2003 - 2004.
I would steer clear of NX100 as well. My company is in a similar position to yours with a used NX100 controller and used robot and we have had nothing but headaches with it. if you do find out if transferring programs/data can be done simply I would love to know because we are looking to do the same next year.