After the wife's last back surgery I bought a set of fully adjustable bases off of craigslist. Together they make a king size bed.
We know what we like for mattress firmness so each of us got the firmness we like. Have less than 2k in the whole works. Wife adjusts her bed a couple times a night depending on her sleeping position. Mine has the head elevated slightly and that is where it stays 99% of the time.
Why pay for more than you need. When I researched the sleep number system what I found out is 95% of those that have them seldom if ever change the setting once they pick a firmness.