You're right why not 0.001 btc if powerful gpus are out of reach? Of course 1080ti would be great because as difficulty rises it will be used for many years and profitable as well. I think 1050ti can be used for 1 or at most 2 years then it won't bring any profit.
What I want to ask is how is it possible for the same gpu to bring twice the earning in a more powerful system? The important component is gpu. Others are just there to let it work. Maybe your old psu did not give enough electricity to the gpu? It worked but could not work effectively is it possible? What do you think?
RE: Update: #2 Dedicated cheap miner