think I have taken the maximum out of the CS2.4I think I'm there, too. If I had ample money and time, it would be interesting to experiment with ultra caps (Jupiter, Dueland), resistors (Path), and try the wax foil coils. But if I had that much money I would probably just buy Vandersteen 7s and call it a day!
I think my modded 2.4s sound as good or better than anything new up to at least $20K and for a fraction of the price.