Any regulator with a range of adjustment of 5-40 psi is fine. The requirement doesn't change with the number of kegs, you just get a bigger manifold. I've got a 4-way and I'm seriously thinking of moving the CO2 outside the keggerator & adding another tap.
the reason i ask is my father gave me a stainless steel regulator, and its rated up to 6000 lbs. im starting to think this is major over kill. am i right?