Vivek, I just found this thread. I am saddened to see you depart the M3 family so quickly. Darn, you've done so much to the car in so little time and won't really have the time to enjoy and appreciate all the great (and $$$) mods you've put on.
The M3 is a great car to start with. With the mods you have, it's an incredible and amazingly capable car. I have not driven the GTR and I am sure it's a great car. From what I understand, although it will be very fast at the track, I am not sure you'll get the same driver involvement you get in the M3.
I've had my car for 3 years now and I can't even think about getting rid of it. Every single day, I sit behind the wheel, start it up, hear the exhaust rumble and cannot stop feeling fortunate to drive such an amazing machine.
Hope you enjoy the GTR. You may want to wait a few months before you dump a bunch of money into it and make sure you want to stick with it. Regardless, I look forward to seeing you at the track next year. M3 or not!
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