i looked at the lifereef overflow, and the design is absolutely solid...i found an eshopps overflow that was the same concept and went with that one because it was less costly. it doesn't take up more space than a HOB filter.
for the flow rate of 600 gph, I found mine to flow slightly less than that out of the tank because I have a hard time removing all the air from the siphon tube...if I did a better job it would probably flow the 600 gph. i run a mag 9.5 for a return and I have a ball valve on the return line to dial back the return flow to a rate that my overflow can keep up with.
FYI, make sure you use a "tube style" overflow box, they don't loose their siphon in power outage situations (mine's been tested 4-5 times already)...the "weir style" overflow can loose the siphon in the power outage and requires the air lifter pump to "avoid" losing the siphon, but i've heard anecdotally that they can still loose siphon, but I don't have direct experience with this type of overflow.
here's a link for the
eshopps overflow....HTH
