underdamped = bouncy/'springy'/riding on the spring
overdamped = "skipping" across the road, no suspension movement, 'harsh'.
Many coilovers can go from underdamped and bouncy to overdamped and cause the car to skip across the pavement.
Monoflex is much better than the Flex, but it'd be hard to compare to JIC without back to backing them. SRC's are tein's best damper but IMO isn't near the quality of damper or have the useable range of adjustment as the KW V3.
HKS Hypermax are very nice coilovers as well.
I love my 2812 except the noise, nothing comes closed... but then I haven't driven the JRZ, drove a KW v3 in an EVO ix, but then i know it could be totally different on nsx :biggrin: