Go with the Illuminas if you can. That adjustability just can't be beat for fine tuning the handling, or for changing from "racing stiff" to "cadillac comfy". I run spring rates of 275f/150r and love the car for both daily driving and weekend racing. If you can only afford to put Illuminas on one end of the car, I would put them on the rear since they seem to make the biggest difference between settings in that position, and the biggest difference in handling when fine tuning over/understeer.
But if you
don't plan on daily driving, taking long trips, etc. then you could go with the Blues and do just fine. You'll lose the fine tuning ability that the adjustable shocks give you, but a lot of time its easier (and sometimes even better) to adjust the driver rather than the suspension.

Here's a writeup I'm working on concerning autocrossing an RX7 that you might find interesting.
http://www.iwankel.com/index.php?option=co...=4&id=10#26Best of luck, and feel free to continue hitting me up with any questions you may have....