Dell is updating the XPS 15 with a NVIDIA 10 series card soon-ish (December?). Any one shopping for a decent dGPU on a light laptop should consider it.
Their current top-end XPS 15 already supports 32GB RAM, a 1TB NVMe, 4k touchscreen and has an NVIDIA GTX 960M. I was looking into it recently and it was on-sale for $2250. Maybe I should wait for the update. I like the idea of having a 15" screen with a smaller form factor (without the bevels).