The RXS-S was an uprated verion of thr RXS.
Amoung the differences:
RSX-S/RSX
K20a2 vs K20a3 (the a2 with 197 {197 hp, true VTEC} vs 160 from the a3 with i-vtec
Stiffer springs
different gearing
differently sized front and rear sway bars
There were also some chasis stiffening bits that I want...