As
@centerpunch noted, NA1 & NA2 refer to the engine displacement - that's it (although some lump the 6-speed in with it as well.) But since so many authorities get it wrong and think it's the fixed headlights or the Targa top, here is a chart, with
NA1 in orange and
NA2 in green:
View attachment 189250
So from the chart, if the OP wants a 3.2 and pop-ups, he wants 1997-2001. There's not much difference between the 1995/6 & the NA2's either, especially with the JDM gear set. And the 95/96's are both cheaper and more plentiful. The 6-speed is probably a bigger change, and the new ABS in 2000 definitely is. But there aren't that many 2000-2001's out there. (USDM 2001 Red on Black: 10)
Maybe we should stick this chart on a the changes by year or a Wiki page somewhere.