First: Yes, you can use KYB AGX or any other shocks with HICAS. It makes no difference. Don't pay attention to the disclaimer, it doesn't apply to the 240SX.
Second: I've had the AGX for about 3 months now with heavy-duty springs, I have no complaints about the ride or handling, both are pretty good. If I had it to do all over again I would have picked Koni's instead of AGX, but only because my spring rates are higher than the AGX is rated for.
Third: Not yet...but give me a few months...
