Jerry,
I doubt the new ProFormance coils will work on the CXII. Uncle Willy is the guy to ask that one. However, after this long "out of it", you'd do good to sell the old CXII and GTAx 1000 and pool the moola on a GTP 1350 and a 250. If it took a little cash to up the ante, so be it.
Not that there is anything wrong with either of them, mind you. I found some yummy goodies with my old CXII. But, as you noted, things have advanced after 13 years. It might behoove you to do likewise.
I now have a GTP 1350, a 250 is in the works and I've added a coupla others, too. Shoot, I even got a bonafide freshwater detector. In order to do this, I sold off my GTA 1000, 1250, the CXII and the others, all but my Silver Sabre uMax - and its going after I get the 250. Every so often it's a good investment to upgrade.
And you can do what I did. Pick 'em up used.
Just my two cents worth. Welcome back, Jerry. Do your research and have fun