I tried the arduino way with no luck, but IIRCit was problem of my arduino board.
Anyway I think it's easy and cheap enough to get a old pentium4, install Mach3 and remote it via Ethernet cable and Remote Desktop. Also Mach3 is supposed to be more powerful than GRBL, not sure why, but I remember to read about that.
There's also PidiCNC, a set of raspberry pi daughter boards to control steppers, servos and provide digital and analog I/O's for the machine, nice for limit switches or control pendants.
It works on LinuxCNC, but seems a bit slow in its development and commercializing. Anyway I think that's the best solution, a full PC is wasted power and space just to run three steppers and a on/off switch for the spindle...
EDIT: as I posted this I looked for PidiCNC web and it seems to be selling the board already, but every product shows 1,20€ and the texts are not in English so I guess they're struggling with the webshop