There is an upflow 5600.
upflow only really goods good if the resin bed stays packed when in brine flow, if there is any way for the media to move it will, thus making the up flow not as good.
The only up flow that I have seen work 100% is the Hague Water Max because of the way the tank is done..
If you can get the USA resin great..
Pre Filter if there is nothing in the water for it to remove would be a wast of money.
You should be looking for a unit with 1.5 cubic feet of resin and useing 9 lbs of salt on the cleaning cycle.