I would DEFINANTLY go for a better radiator.
A standard heatercore will surely outperform that radiator with a large margin. These can be had very cheaply if you find the right place.... upgrade upgrade upgrade !
Im going for a Volvo240 heatercore as they are easy as hell to find around here in sweden ( volvo240 is probably THE most common car here) I think I´ll be able to modify it to fit into my case aswell ...
Just for the record im now using/testing a lowpressuredrop radiator from hayden which works okay to i guess...