I have the Flex -a lite....dual puller 220 fans...bought them from Summit racing for 189 i believe. No need for the relay or anything.
I have mine wired to run all time car is running. Works great. No battey problems, no colling problems at all. I am at BPU. They bolt directly into stock radiator.....very easy. As for power increase...not sure on exact.....but imho has to free up something.....in the end.it all adds up!!!