Having more pistons per caliper doesn't really do much for overall stopping power. In terms of sustained use of brakes then you might want to get a larger caliper w/- more pistons, but seriously when was the last time you did 20 straight laps of a circuit going 10/10ths?
If you are worried about your car hauling up, then get rid of weight, and get a bigger front footprint while braking (suspension anyone?)
Aside from that, the best advice I can give you is the advice Possum Bourne dished out - that is make sure that your brakes are mounted BLOODY well regardless of what you get, if you decide to get RX-7/R33/300ZX/WRX calipers and use a custom plate to mount them then make sure you get someone with a good rep to do it.
Oh and Hilux calipers are pretty hefty beasts, you'd be adding alot of unsprung weight to the fronts!!!