5 x 1000gph = 5000gph
If money is no object and you are going for the lightest, more compact system then we dont need to go any further but if money is an issue and you dont mind a couple pounds more then you might want to explore the option of running a couple cheaper pumps.
An added plus of having more than 1 pump is redundancy in case one dies, that way you dont have to drop what your doing.
Look at the amp draw of the larger pumps, running a couple of the 1000gph pumps together running about the same draw will be cheaper.
If you go higher your time to run will change.
What are the specs on the battery that you are wanting to run and how large is that?
If you just care about size and weight and not money then here are a couple good pumps to look into.
Rule 4000gph
Rule 56D, Bomba Submers. 4000 gph (15550 lph) 12V
Rule 8000gph (two 4k pumps together, like I am suggesting with the harbor freight / hydro pacific pumps.)
Rule Industries - Rule 8000 GPH Bilge Pump