Very true!
But if buying new that's not an option, 70k second hand brings a vast amount of options, infact I think that could be 430 money and Lambo money as well. Or R8 V10. The downside is these all will no doubt have far higher running cost than the three new cars without a doubt, no warranty and servicing is a lot more on Ferrari by miles.
Have you looked into the running costs? As I understand it the GTR is very expensive to run, servicing, brakes etc - in the same league as the supercars you mention, where say a GT3 may not cost much more than your current 911 to run.
The GTR will certainly empty your wallet a lot quicker than a cayman.