Well in order to best answer that question, it would be nice to know what HP you are shooting for.
The stock SMIC apparently does little or no good for the car, a lot upgrade to something liek an MKIII Supra SMIC, which cools a lot better. If you go to
www.silvia.com (I belive) they have reviews on different SMIC from other cars.
Another intercooler I found out about on
www.sxoc.com (its a UK 200SX board) thier cars come stock with CA's so they know more about em. Well anyway they use FMICs from Saabs and Volvos, I know the saab intercooler is good up to i think 300HP, and there is a company that sells saab parts, and started selling the FMIC with piping that fits the CA18 (this happened due to the amount of people buying intercoolers from them. I think it was 75 pounds + shipping, but not positive on price.
If you go to the SXOC message board (it's under community on
www.sxoc.com) and just search for Saab FMIC, there will be a few posts on it.
Also go to
www.h-dev.co.uk they have a full install on the intercooler with SAMCO piping.
www.salvogroup.co.uk is the company that sells the fmics