On the opposite side of the cost spectrum is the upgrade heat exchanger put out by David Wilks link . Looks pretty good to me, particularly with the fan option. David claims that " Average coolant temp drops have shown a decrease of 125 degrees. This is during full boost of 18psi and on a 95 degree day."
OTOH, JT says he hasn't seen much benefit from his, but I don't believe he has any fans on his big exchanger.