At some point i couldn't afford a honda, till i got a job and bought me a cheap little integra for 2k. I then got a better job and bought me a better can and this trend continued on for a while till i was able to afford my Z, and i always loved each and every one of my cars.
So i guess my point being, even if you have the money, you dont necessarily NEED to buy the next big thing. You obviously got the car because it appealed to you at some point. And there will always be better STOCK cars out there than a GTR like the new lambo. Instead of dropping 100k on a new car why not just modd the Z, make it unique. Make it faster than a lambo if you can.. Possible? Ehh prob not. Who knows, But that would be cool to see!!!
or at least thats what id do. Make something of my car, not just give up on it every time i can afford a better one. Just my 2cent. Hope it helps.