ive been using an autozone "TORQFLO" fan clutch, as recommended to me by "BURGPATH" several years ago
i believe it ran me about $60 or $70
it blows harder than stock, for sure, and comes with a lifetime warranty.
It did eventually fail after 3 years of hard use, (much shorter life than stock - possibly because it engages much harder than stock) but autozone gave me a brand new one for no additional cost (aren't lifetime warrantys great??) so i cant complain much about that.
it blows so hard, my qx4 sounds like it has a turbo whenever my ac is on, or, if its over 85* outside. Last time i went camping, i pulled up to the camping site and one of my friends, who works on cars, says to me "whoa why is your engine fan blowing so hard???"
i recommend it for performance but not so much for longetivity