As you can see from the preceding lists, the system administrator has a fair bit of work to do to help install and maintain the SugarCRM system.
This should tell you that whoever you choose as the system administrator needs to have some time available to complete these new responsibilities. Also, the administrator must be someone who can be trusted with all the user access information and with the company's most sensitive data, as the administrator can see all the data in the entire SugarCRM system.
Many businesses choose the same person who administers their PCs and their network as their system administrator. In smaller businesses, this person is frequently a part-time contractor, not an employee.
If an outside contractor is already administering all your network access information, it doesn't really make things any worse to hand them the keys to the CRM as well—so if that's your inclination—go ahead. However, make sure you have a good non-disclosure and non-competition agreement in place with that contractor.
The tasks themselves do not require serious technical skills in order to properly execute them. With a little technical advice, a senior manager in the business can fill the role of system administrator just fine—although it may not be a good use of their time to be resetting user passwords. However, they will have the knowledge of and the control over who is accessing the business's key data within the CRM.