I went through the same thought process as you 3 years ago.
1.Still loving my car but wanted more power.
2.Bought the car new it's now 4 years old but still seems new,but offered crap money part x.
3.Looking around at what other cars are available used for my new budget,but they are maybe older,have more miles,unknown history,wrong colour/spec etc.
4. Going to loose a lot of money on the mods.
I came to the conclusion that my choice was either to modify my Zed to a very high standard and enjoy the journey over a few years and end up with a very rare and distinctive car or buy an early GTR,leave it alone and hope that nothing goes wrong!
Even now with hindsight on my side the choice is just as hard,but if money is no object the GTR wins hands down because of tuning potential of that car the world is your oyster.
The only thing I have to say is that people expect to be blown away by a GTR or any other mainstream big power car but there is nothing more satisfying than making a very expensive car go small in your rear view mirror or blasting past them on track with something that by rights should not be going anywhere near that quick Is one hell of a buzz!!
Unless you buy a bomb proof classic cars will always lose money so go with your heart.
I know it's not a 370 but if you want to have a blast in my car drop me a pm.
Good luck