I don't' believe you can break that down any further, the permission you're referring to will allow the users in this role to modify any of the VM devices which includes HD,NIC,etc.
=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at:
Twitter: @lamw
VMware Code Central - Scripts/Sample code for Developers and Administrators
VMware Developer Comuunity
If you find this information useful, please award points for "correct" or "helpful".