All i know is that when i called them a few months back to enquire about lowering they did say that it would improve the handleing as well as lowering the ride height
Fact is dude that the spring rates of the H&R and Eibach set-up tell you what to expect. It's a fair amount of work to change the springs on a Meg so if you're going to go to the trouble of changing, and you want to improve the handling, then you might aswell do it properly or not at all.
You do a fair amount of track work and not a huge amount of road driving wwith it so you're a prime candidate for some V3's, AST's or Nitrons imo.
The coilovers listed in the first post might have a reasonable reputation in other circles but the spring rates for the rear look retarded (so retarded that I suspect they're wrong). Would want that clarifying first really.