what are you trying to achieve with the car? major slammage or a just a mild nice comfy drop?
Megan's can go low but I have read and heard that the springs are too soft if you want to run an aggressive fitting wheel, if you want to add bigger wheels and slam then I recommend stance or pbm, if not then megans will suffice, as for RCA's those are still new to me so i can't help there, all i know is they stand for roll center adjusters but not really have any clue what they are as i havent researched about them yet. anyways good luck with your car!
98 GS400, slammed, drifted, daily'd