The latest ROM update for the X50V with WM2003SE is A05 which can be found
here.
The programs listed in my particular MyPDA are just what I personally use or have tried. Your needs might be different, but its a good place to start. I also have links to a few great (IMO) MyPDAs from other aximsite.com members.
Some people have had problems with the upgrade to WM5.0 from WM2003SE, so I would just stick with WM2003SE as it is reportedly pretty stable. See how you like it first and if it works for you then no need to change.
Good luck with the process.