Ideally you want a sump design where you can redirect some of the flow around your DSB. That way you can fine tune your DSB flow rate, and have a higher turnover return pump. Personally I'd go for more like 10-15x, i.e. 5000-7500 l/hr effective, which given a head of about 1.4m means you need a pump nominally rated at more than this.
As an example, here's the flow graph for a pump nominally rated at 450 l/hr, but with a 1.4m head it only achieves about 300 l/hr.
Info: Pump Head vs Flow Rate - Overclock.net - Overclocking.net
In summary, I think you'd be well served by a Lifetech AP5800 or similar pump. It's rated at 12,000 l/hr, but probably achieves around 8000 l/hr with a 1.4m head and some piping, which is around 16x your system volume. Provided of course that you divert some of that flow around your DSB, as it's probably too much flow for that.
You could also install one of those clever-dick flow mechanisms at the outlet (I forget the name) to create varying, turbulent flow in the display tank.
Q