Ok, just watched some review just now, but 1660ti is performing like a 1070 FE, a custom 1070 will outperfrom 1660ti, so I guess the 1660ti goes off the list.While all 3 options will slightly outperform the 1070, I wouldn't view any of them as a worth while upgrade. And I don't think you'll gain enough performance to make it worth the 300+ you'd spend. Just imo.
Unless you want to use RTX for deep learning, cryprography (much faster with integers than 1070 thanks to the tensor cores) or really want to have raytracing in games, I think you should wait for a next generation of GPUs. You will get only several percent performance improvement with these options and you will spend $300. In my opinion it's not worth it. Take a look at some comparisons and benchmarks:I currently have a msi gtx 1070 gaming x and need some help regarding to which gpu to upgrade and I have 3 options:
Rest of the pc is: 8700k, 16gb ddr4 3000, evga 550w.