For the thread starter, well all i can say is go for it, and just make sure you are not using more than 30% of your salary to maintain/modify the car, always save up for a rainy day.
And once you get your dream car. First thing is to make sure you install all those high tech security alarms, and of course never park your car in a non guarded place.
Try to be low profile as possible, try not to show off your car too much as it might get a lot of attention. A lot of attention= bad, as lot of envious people out there might come up with some bad bad things. Also, always educate your self with knowledge before choosing the car, get a forman to inspect the car before buying it, and after when you suspect problems with your car, try to do your own research so you might have an idea to pin point the problem yourself.
The sport car I suggest , well since most other users posted good suggestions such as silvia/fd2r
how about this? something rare?
http://www.infinitiinthenews.net/infiniti-g-line-adds-performance-coupe-g25-sedan/
the g37 roadtax would be an overkill, so thats why i suggest the 2.5, but of course i doubt it would be more powerfull than a standard s15/fd2r