the misimoto i have heard good things from the evo guys about, they are like dirt cheap and have said be to actually decent quality.
its understandable that the koyo are expendsive, on my partular application my koyo rad leaned against my turbo and it melted 3 of the core bard in 2 places, and i tried a few different oem radiators and none of them could keep my setup cool, always ended up running hot, i had the radiator repaired and put it back in with 1 pusher fan and the can runs perfectly cool now... its almost lik i would have no choice but the koyo since nothing would keep my setup cooled down