The GTX 1050Ti does not support SLI, anyway it is recommended to switch it off for 3D rendering.

Recommended PSU wattage refers to your complete system. Your GeForce GTX 1050 Ti draws just 75W max. Play with the power calculator - add / change the GPU and compare the results. See your system power demand without a discrete GPU (presuming it will use the in-built processor graphic controller).

For GPU 3D rendering you should be looking for a GPU with max. number of CUDA cores (shading units), max. graphic memory and min. power demand. Adding another 32GB RAM to your motherboard will not help your GPU(s).

Talking with your retailer before spending any money would definitely be a good idea.