Hi,
If you are going low tech (low light, no CO2, no liquid carbon and minimal ferts), flow isn't as important as it is for high tech aquariums. So I'm not sure that you need one let alone 2 Koralias.
With 3200 litres per hour that's well over 10 times the volume of the aquarium. We use the 10x rule for filters knowing that in real life, a filter circulates about half of their stated flow rate. However, flow pumps don't have such restrictions caused by the hoses and filter media.
To advise you more, people also need to know if you have a spraybar or not and where the filter outlet and intake are in the aquarium.
Cheers,
P