300's are getting a bit old now and as mentioned in other posts, the engine is a nightmare to work on. Being an older car, there will be SOMETHING that will need replacing/maintenance in the engine bay and it's going to give you headaches.
Depending on your budget, I think the later the model of car you can buy the better. I don't like R33's much myself but if you could pick up an N/A series 2 R33 it would be your best bet. The later the model the better.
Second choice would be an R32 GTS25 (RB25DE) but once again they're getting a bit old so be prepared to fix a few things. Plus side is theyre usually easy as pie to work on, so it wont cost you as much.