Water softening is a commodity process. There's no magic or special sauce.

So what you are left with are three things:

1. Decent hardware

2. Service -- if you want or need that (Ongoing)

3. Correct sizing, setup, installation, etc. (one time)

Some people need a lot of hand holding, others can do it all just fine themselves.
If you are willing to configure it and such and don't need a lot of hand-holding then I would go with units from 602ABC water on Amazon.

They feature Fleck control valves which are very reliable. You can order with 10% crosslinked resin (if you are on city water). My 48k grain unit was about $550 delivered.

I don't have any relationship with the company other than being a customer - I am very happy with my purchase 2 years in. That cost is almost 1/4 of your most expensive quote.

A 48k grain unit (1.5 cf) should be about right. If you de-rate that based on 10# of salt per cf instead of 15 then the softener capacity is now about 40,500 grains. That would give you about 8 days between regens based on 4 people and 60 gal per person / day.

Know that it will require some settings on the valve. You really want to set the salt settings at 10 pounds per sq ft instead of factory 15 pounds.

The folks at 602ABC water can help you out - they have instructions for setup and can step you through specific questions if you need it.

Thanks.