Going to be getting a new sport car.?
The 300ZX is a wonderful car, but is a huge pain to do work on it.
An Eclipse would be ok, but make sure you have the transmission looked at before buying, they do have transmission problems.
A Mustang wouldn't be so bad, but since you are only going to pay 10K it will probably be high mileage.
If you live in the USA, then Skylines are not sold here. GT-Rs have only been sold in the USA. I've never personally seen a Skyline outside of the USA.
A RX-7, those are pretty old, you could probably buy a RX-8 with that money. The main problem with the RX's is that they are not fuel efficient, not by any means, ans the RX-7 is know for also burning oil, they are truly amazing cars. I just test drove a RX-8 and the handling was just amazing, but the rotary engine was keeping me back from buying it. I personally liked the 9K RPM redline in the RX-8, but again not worth the money.
If I were you, I would also look into a 240SX and really fix it up, those can be made into hella fast cars.
Good luck man