Alex,
Master needs to run the robot.
I your case it really doesnt not matter that your Media servers are connected to the SAN, they are just using the disk space on the SAN array.
SCSI attach the master to the library, robot is SCSI ID 0 is, then the next tape drive is daisy chained to the robot. < this is a default config.
Configure these two componets to work with your master, take the next tape drive an conncet it to one of the media servers.
Or
You can buy
http://www.crossroads.com/Products/StorageRouters/Crossroads6000.asp
SCSI FC router.
Hook it into your SAN, then get a SSO licence for you Media Servers.
Unfourtunatly you dont have much hardware to work with.
JD