Not sure about your pipes - but you can go two ways..
Either go for a "performance" radiator which could be something like a mishimoto - or go OEM.
The gains aren't that different and most are under the opinion that an OEM radiator does just as good a job
There is a post somewhere regarding types of radiator - have a trawl through and you might find it
Also put something up in the "Wanted" section - perhaps Si or someone else has one going for sale
Ryan