After reading a post about which format to rip into, I decided that the best thing to do was to rip all audio to flac format. This is lossless which means you don't lose the (theoretically) unimportant parts of the sound that you do with lossy compression such as mp3, wma, m4a etc. Of course this means that the resulting files are much larger - about 20-30Mb each but the advantage is that you will never have to re-rip when a better format comes out in the future (if it does at all), you can simply convert your flac files to the new format which will result in exactly the same quality as if they were ripped from CD but much, much quicker because they are on a hard disk rather than loads of CDs.
Since hard disks are cheap now, unless you have millions of CDs, they will only take up a few 10s of Gb of space and save the re-ripping.
My plan is to put them on a server in my house and use the full quality files for playing in the house and then convert them to m4a format for my mp3 player and laptop.
By the way, KAudioCreator will not rip to flac straight out of the box even though it is theoretically set up to do so. You need to install the flac encoder which you can get simply with the command line: "sudo apt-get install flac" If you don't have it installed, when you select flac, it will start ripping and then fail when it tries to encode the file.