As far as current in the tank I say get the best you can afford. I had a Korallia and I was not impressed with it at all. The impeller do not disperse the flow correctly IMO. Remember that the better pumps are controllable, the Vortech is supplied with it and the Tunze single controller is pretty cheap. Once you get the Korallias that are controllable, plus the cost of the controller, the price is not that far off.
My vortech, I run on full blast because the flow is very wide and does not blast the corals, even the ones that are within 6 inches are fine. My leather loves the undertow it creates as well. The Tunze is a little more concentrated, so I run it on a single controller between high and medium high(1875 gph to about 900 gph) for 5 seconds alternating. I do plan on replacing my Tunze with another Vortech MP40 and I plan on running them on long pulse mode, one master and one slave, opposite eachother for about 7 seconds alternating.
I wish I did not waste money on half the crap I have purchased for this hobby. Do it right the first time, it will save you a lot in the long run.