I've been doing more research and leaning toward buying a system that's a little oversized for our needs atm. Re-doing the math:
Daily usage at ~200 gallons. 200 gallons per day x 10 gpg hardness x 14 day regen = 28,000 grains.
Is a 14 day regen too long? Should it be more frequent? Thinking Fleck 7000SXT Valve and a 2.5 cu ft system. Any input appreciated.