Yeah, thats what I saw. I have a Mag 7 I'd like to use, and it seems the mazzei will let me do a much better skimmer with a pump that size. There is one thread on RC where a guy built one, but it didnt really have any plans.
http://reefcentral.com/forums/showth...p;pagenumber=1
From what i've read, it seems the 584 is the most common choice for a 500-700 GPH pump, but apparently there are lots of different ones that vary in the GPH/PSI they want for optimal performance.