We have just gone through this process ourselves after importing a reasonably stock R33 GTST. The first thing we wanted was to do some mods - but when you sit down and actually add up the cost of mods (FMIC, Computer, Injectors, Turbo upgrade, Fuel Pump, Manifold, Wastegate etc.) it is ridiculous !!!
We have now sold that skyline after much debate and are in the process of importing a highly modded 26DETT R33 GTST - we could have no doubt afforded a stock R32 or R33 GTR - but again we would have the same problem in wanting to do mods.
Our reason behind our final decision was anyone who owns a GTR has an awesome fast car - but to have a GTST that will be able to compete with most GTR's is a special awesome fast car and it's nice to be different sometimes too.