I have the hardware for a eGPU setup
Macbook ProRetina 13" Late 2012
Galax GTX 970
PCIe x16 Raiser
I used @goalque's script to setup OSX too, but was sad to realise that the internal display in Mac cannot be powered by the eGPU, had not planned to get a new monitor
And was not so sure about the Windows route - 25-30 GB free in SSD + Windows OS + @Tech Inferno Fan Setup 1.3x script even after which an external monitor is a recommended approach.
Needs some advice please....