Another reason why owners of Sony cordless telephones are reluctant to "upgrade" is that they can't find anything with better range. Nothing can beat a 900 MHz cordless phone for outstanding cordless phone range and that includes the latest DECT 6.0 cordless phones.
Before getting out of cordless phones to build Playstations and TV's, Sony released a line of 2.4 GHz phones. Sadly they were pretty ordinary and had the same issues as all other 2.4 phones. They were far from being the best Sony cordless telephones.