Once the CS is on version 8, you can push the upgrades for the rest of the environment in version 8 and in the interim run the media agents and clients at 6 or 7. In 8.0 the Update Cache has also been incorporated to hold the CV software allowing for upgrades to be pushed from the CS GUI, with some exceptions, such as clusters and SharePoint. The directions from the link below starting at step 3 will instruct you on 2 ways to populate the update cache with the CV software. I would suggest using the manual method of creating the directories and copying the software. Please note that the DVD(s) are pretty big in size so make sure you have enough room or relocate the Updates Cache in the Automatic Updates settings. Once the software has been copied over, you can then follow the instructions to push out the upgrades.
***Make sure you are using the latest installer package which can be downloaded from Maintenance Advantage.***