Single resin tank softeners are generally set to regenerate at 2AM. It would be a RARE occasion that your RO would be generating RO water in the middle of the night.

You can rest easy and replace your single resin tank softener with another single resin tank softener. Just avoid pre-built box store softeners and get an industry standard design... it's the best bang for your buck.

Good. Dual tank will not be a priority. I am leaning toward a Fleck 2510sxt and Apec RO. For comparison, I have Kinetico coming on Saturday. I may be back with followup questions after their visit. Thanks.

Fleck 2510SXT is a good choice IF the softener is correctly sized and set up for efficient operation.

Is the Apec RO made in US with US components or just assembled in the US with foreign parts?

For sure, correct set up is something I am not ready for, at this time. I will be by install time. Regarding APEC, they say their membranes (Dow Filmtec) and filters are manufactured in the US, and their systems are assembled in the US. If you have any bad experiences with them, I'm listening. If you have a good recommendation for an alternative I would consider it as well. My big picture plan is to put the RO system in the basement right under the kitchen feeding a faucet and refrigerator, with a 10 to 14 gal tank to support our heavy coffee, water, ice, and cooking habits. Our water pressure on city wateris 55 psi with the softener in its current bypass state, so I'm also concerned about final RO pressure to the fridge. My research continues.

When a seller says assembled in US it means they are using few or no US parts. Have had problems with pacific rim filter canisters splitting and poor quality control with fittings and connectors.

55psi should be adequate but some late model fridges don't like the low er pressure output of ROs... especially fridges with built-in filters. Usually there are ways around that problem.

Correct softener sizing is best considered BEFORE choosing a softener. Efficient set-up is a part of correct softener sizing and is determined by water conditions, occupancy, # of bathrooms, and other considerations.