The Fox you have listed is for 29" wheels, not 26" like you Haro has. The appropriate fork is this one:
http://www.foxracingshox.com/bike/10/forks/32_F-SERIES
Although, you don't need their top flight XC fork, especially since you're putting it on a not light bike to begin with. I'd suggest you go with the slightly heavier, and much cheaper Float:
http://www.foxracingshox.com/bike/10/forks/32_FLOAT
The Reba is also a nice fork, and highly adjustable. However, it has a simple port orifice rebound circuit compared to the Fox's shimmed rebound circuit.
Both the Reba and the Fox products are mature, and you won't really be looking at any serious problems. Both will require maintenance, with the Fox requiring more because of their crappy seals.
If you don't mind doing the maintenance, then buy the Fox. If you'd rather just ride and not worry about it, get the Rock Shox. If you don't care one way or the other, buy whichever one's cheaper.
KHS doesn't make suspension forks. Why did you think they did?