As with kenosmith3, I just went through this process myself. Due to a couple of software issues with the version of SAM we had, I decided to go with latest and greatest releases. The only issue I ran into was NCM. I found that with not being on the latest NCM prior to the upgrade, I had issues when it came time for NCM to consolidate the data into one database. The solution for this was to uninstall NCM and install the previous version I was running, then upgrade it. NTA went fairly smooth for me going from 3.11 to 4.0.3. We actually set up a completely new environment with SQL and all, so I started by restoring a backup of the database to the new SQL server, installing the latest of everything except NTA, getting all devices changed to the new polling server, removing the old polling server, then upgrading NTA. Once this was done is when I found out about the NCM issue and ended up uninstalling NCM, purging the install folder, installing the previous version, then upgrading. I wouldn't necessarily say you have to start with the same version as your current server, I didn't, but I WOULD when it comes to NCM in order to make sure that upgrade goes smoothly.
Also, as kenosmith3 states, don't forget the Reports, NCM Config Archive, Templates from the install directory, and any custom logos you added for the SolarWinds website from the inetpub folder. Just make sure you have the new environment ready, and for NTA, if you are not already on v4, make sure you have a separate NTA database server available. You do not want to put that on either the SolarWinds or SQL server unless you want a mess of performance issues.
-Matt