Not sure what happened to Curve to be honest, I believe Kona bought the rights to the name for their own brand of components on the '96 bikes, notably the chainsets and brakes (which also seem to have a bit of an iffy reputation, mostly for flexing and being a pain to set up). These components had been dropped by the next model year.
As for replacements, there's plenty of choice - my Kona and GT (95 and 97) are running White Industries and Middleburn RS7 cranks and I've had no problems with either. The Sugino Mighty 900 cranks fitted as stock to the '97 Explosif are also pretty cool I believe, but a bit hard to find. Hope this helps
Several bikes, one supportive lady and still trying not to buy anything else!