You can get two 10" slim lines for about $50 each and wire them up to a relay and use the stock turn on wire to turn on the relay and it will work fine. Two slim lines will definetly work good enough without shrouding.
You can do 12" fans too if you want, get a puller behind the radiator and a pusher in front of the radiator if there is space, if not keep two 10" pullers behind the radiator.