Plenty of information on SSDs in Cubes over at the CubeOwner Forums. Have a look at http://www.cubeowner.com/forums/index.php?showtopic=14640
No great drama in getting past the 120GB linit on HDD size, again CubeOwners Forum has http://www.cubeowner.com/forums/index.php?showtopic=13148
And as you've already got a 400GB drive in the Cube, it would seem that you've got the "fix" already applied. Just check out the information on partitioning for the new SSD you're intending to put in.
No great drama in getting past the 120GB linit on HDD size, again CubeOwners Forum has http://www.cubeowner.com/forums/index.php?showtopic=13148
And as you've already got a 400GB drive in the Cube, it would seem that you've got the "fix" already applied. Just check out the information on partitioning for the new SSD you're intending to put in.