981 GTS to GT4 or 991.1 GTS is the only way to go
981 GTS > GT4 - I have been in my friends one and from a monetary stand point its not worth the extra £30K for a little bit better performance plus I know ill get some stick for this but I also prefer a PDK.
991.1 GTS - I've looked but its finding one with a spec which fits my requirements.
However, the big difference for me is I can get the 991.2 GTS in a spec of my choice. I think a week in the 991.2 should be more than enough in my mind to see if the car is worth the upgrade.