How much head is in your system?
If it's less than 10' there is really no reason to go with a high head (hi pressure pump) like the one you linked to. That pump draws 700 watts (x2 = 1400 watts). Unless your plan is to run your sump 15' below your display tank (ex- in your basement) or are pushing water through canister filters before back up to your display, those Little Giant (energy hog) pumps are totally unecessary.
There are much more efficient options out there that will give you comparable flow, on much less wattage.
If you only have 6' or 7' of head (which is more common on standard sump setups), then I would go with two Laguna Max-Flo 4200s. They will each give you ~2,900GPH at 6' of head, so running two would give you 5,800GPH...the best part is that each pump only draws 160 watts, so you are getting almost as much flow as those other pumps, while using only 320 toal watts (a saving of almost 1100 watts).
Another option is the AquaSurge line of pumps; they are also very efficient, although I've never used them so I can't vouch for them personally. I know the Lagunas are good pumps...I have two Max-Flo 4200s and am very happy with how quiet and efficient they are.
http://www.azponds.com/New_webpages/New_subpumps_Classic.html
Make sure your drains are large enough to accommodate that much flow; 5,800GPH is a lot of water.
) but i live in a small 1 bedroom apt.. so hoping my elec bill is under 80.00 this month!! oh and then i had 4 tanks running ( last summer, two 55s a 20 long and a 10, sometimes a 20 tall ) now i have two 55s one 20 long one 12 eclipse, soon to be more tanks..