arghhhhh
Imperial Gallons rather than US Gallons! I think you'll find they show both on their site specs.
http://www.eheim.com/technik_pumpen.htm
I'm still at a loss as to why people require such huge flow rates. If you are using an air cooled rad with a smallish system coolant content you will push the coolant through it faster than it can release the heat properly if the rate is to much. Of course too much is better than not enough as you can always restrict the flow but I would think 250 GPH (imperial) should be enough for just about everything, as long as it is split in a manifold and you dont have any major pipe restrictions.
My cooling system works a little differently (no rad) so maybe that has something to do with it, but I noticed ZERO difference in CPU temps Before when the pump output just went through the CPU block, and after fitting when splitting the flow to a manifold and supplying CPU / VGA GPU & Ram, & mobo Chipset.
This indicates to me the original flow was in excess of what was required, and with the now slightly reduce flow rates it is still as good as it needs to be. This is using an Eheim 1250 pump which is also pumping up about 1.5 meters.