Yes,
but it is better to decap them so the media can clean the pockets and even the flash holes.
If you decide to go with SS Tumbling, you might want to get a larger tumbler for the volume.
(I have no idea how well made the RCBS is, nor if it has a thick rubber liner like the Thumbler's Tumbler has. But then, The Thumbler's doesn't cost $546.95 )
You might want to consider a cement mixer....