Consider using LinuxCNC with a Mesa 7i76e ethernet motion controller. 5 axis step and direction, 32 inputs and 16 outputs from memory. Either stick with your Proma or consider the Mesa THCAD addon card for USD $69 for torch height control. Either option is supported under LinuxCNC.
I'm just finishing off my plasma build with the 7i76e/THCAD that I've built from scratch. I just have to turn the pile of steel in my garage into a table.