There is a file in the repo called packages.txt that does, in fact, list every package on the iso. It only covers the Standard version of the distro, not the Light, SOHO, or Live variants. DistroWatch also track major packages and gives you a side-by-side comparison of the versions from 3.2 through 6.0 Beta. It isn't comprehensive but it does include all the major packages. It also does include SOHO.
Personally I found the improvements in 5,9 compared to 5.8 to be huge. If you want KDE I'd go with 5.9.1 SOHO and then do the upgrade to KDE 3.5.10 from the repo. 6.0 is not ready for prime time just yet and the first beta is what you'd expect for a first beta: lots of issues. I think 6.0 will be a great release but it's not there yet.