My 2 pennies worth.
I looked at all the cars you are mentioning except for the rcz, its a Peugeot and will always be.
My missus has a TT tfsi, nice car, well built, solid but boring and loads about. Yes its quick and I'm sure the rs is a monster, but you can now spec a diesel tt to look like an rs so nothing special in my opinion.
The cayman is a really nice car, i was so tempted but struggled to find exactly what i wanted plus price and spec varied so much and still a little boring for my taste.
Then we come to the Z. Having previously owned a 350 i was yearning for a jap v6 again. I had a v6 in an A4 bit was quite tame. I wanted it basic again and the 370z met everything. Its a great drivers car, enough aids to help but still lets you make little mistakes to make you be in control.
Getting a Z also means your part of a select group of people getting the nod past other Z cars. I love it, i love Jap.