I have that discontinued Merlin Garden Pro with all the options... Tall Blue pre-filters, electronic shutoff, digital PPM meters showing incoming and outgoing levels, etc.
I have mine set up to an eighty gallon holding tank, and it works fine for me. I have a similar size (wattage) grow setup. My well water comes out of the ground at 125 PPM and is down to 2 PPM once it passes through the purifier.
I imagine the replacement unit, the Evolution RO 1000, is also nice and will work for your needs.
I'll probably replace the Merlin with one of these some day. 2:1 waste ratio is better than I'm getting for sure. Looks like you can add the booster pump and get it to put out up to 1500 GPD.
That is my suggestion. Hope it helps. I also suggest you get an inline TDS monitor. It is very useful to see how well the unit performs new so you can monitor the TDS to determine when to change or clean various filters.
