I echo that nicely maintained/properly restored S1's and S2's are going up in value, frankly asking prices for really nice ones can be higher than a nice V8, and certainly more than a G body Turbo and Stevens Esprit.
As for the JPS being of more value, it's kind of like the JPS Europa. Mechanically the cars are no different than their 'plain' brothers, it's all in the livery, and provenance. There is a JPS Esprit that pops up from time to time that belonged to Mario Andretti, having been given to him by the factory when he was driving for Lotus. Certainly THAT specific car has some extra cache.
I don't suppose your car has been languishing in Maryland for the last two decades? Phil Mitchell's been trying to sell his in-need-of-restoration JPS Esprit for years, I heard he may have recently off-loaded it. Was it yours?
Have owned, enjoyed, appreciated, and now all gone:
1969 Europa S2 Blue
1970 Europa S2 White (my first)
1974 Europa Twin Cam Special Light Blue
1974 Europa Twin Cam Special #4380R Indigo Blue (my absolute favorite).
1984 Turbo Esprit Calypso Red
2005 Elise Starlight Black
2005 Elise Saffron Yellow
2005 Elise Ardent Red (used as development mule for the LETSLA)
2006 Exige Graphite Grey
2007 Exige S Canyon Red (first customer installation for the production LETSLA)