I too came from a 300zxtt (with stage III+ jim wolf, stillen goodies). kept the 300zx for a couple of years after buying the NSX, but found i just never drove it. great car, i'd take one again in a second, HOWEVER..........
if you're looking for something to mod for massive HP, the supra MKIV wins hands down. the internals and fuel delivery system of the supra is so overengineered it's much cheaper and easier to get serious boost. the 300zx you need to start replacing the fuel injectors and upgrading the intercooler and turbos to get into same upgrade territory as the stock supra engine.
i just swapped cars the other night with my boss, he has a stock MKIV, it was very very similar in feel to the stock 300zxtt.
if you're looking for something to mod for massive HP, the supra MKIV wins hands down. the internals and fuel delivery system of the supra is so overengineered it's much cheaper and easier to get serious boost. the 300zx you need to start replacing the fuel injectors and upgrading the intercooler and turbos to get into same upgrade territory as the stock supra engine.
i just swapped cars the other night with my boss, he has a stock MKIV, it was very very similar in feel to the stock 300zxtt.