At this point, I would consider the gSC10 obsolete. It technically can run the latest core module, but I have heard some people having a tough time getting it updated without headaches. The 7" touchscreens are likely paperweights, especially if you are going with Crestron. They will work with the latest Nice software however if they are the TP7 and not TS7.

The S1616a can work as a "dumb" amplifier by changing a setting from the front panel, IIRC. No way I know of to control it externally, aside from IR. In an Elan system, it required a ViaNet adapter which is Elan's proprietary control protocol, likely RS485 or 232, but no published commands that I know of.

I would probably recommend replacing all of it and starting fresh with gear you are familiar with and can support.